Project Overview

Dataset: E-commerce Purchase History from Electronics Store (Source: Kaggle)

Project Objectives

  1. To explore and clean a large-scale e-commerce purchase history dataset.
  2. To analyse customer purchase behaviour based on product, brand, category, and price.
  3. To build a classification model to predict whether a purchase is high-value or low-value.
  4. To build a regression model to predict product price.

1.0 Data Exploration

1.1 Install Required Packages

The packages below only need to be installed once. This chunk is set to eval = FALSE so it does not re-run every time the document is knitted.

install.packages(c(
  "tidyverse",
  "lubridate",
  "janitor",
  "skimr",
  "naniar",
  "DataExplorer",
  "caret",
  "rpart",
  "rpart.plot",
  "randomForest",
  "Metrics",
  "e1071",
  "pROC",
  "klaR",
  "corrplot"
))

1.2 Load Libraries

library(tidyverse)
library(lubridate)
library(janitor)
library(skimr)
library(naniar)
library(DataExplorer)
library(caret)
library(rpart)
library(rpart.plot)
library(randomForest)
library(Metrics)
library(pROC)
library(corrplot)

1.3 Load Dataset (Local File)

The dataset is loaded directly from the local working directory. Place kz.csv (raw data) or kz_cleaned.csv (cleaned data) in the same folder as this .Rmd file before knitting. The chunk reads the raw file if available, otherwise it falls back to the cleaned file. The cleaning steps in Section 2.0 are safe to run on either version.

col_spec <- cols(
  event_time  = col_character(),
  order_id    = col_character(),
  product_id  = col_character(),
  category_id = col_character(),
  user_id     = col_character()
)

if (file.exists("kz.csv")) {
  df <- read_csv("kz.csv", col_types = col_spec)
  message("Loaded raw dataset: kz.csv")
} else {
  df <- read_csv("kz_cleaned.csv", col_types = col_spec)
  message("Loaded cleaned dataset: kz_cleaned.csv")
}

glimpse(df)
## Rows: 2,633,521
## Columns: 8
## $ event_time    <chr> "2020-04-24 11:50:39 UTC", "2020-04-24 11:50:39 UTC", "2…
## $ order_id      <chr> "2294359932054536986", "2294359932054536986", "229444402…
## $ product_id    <chr> "1515966223509089906", "1515966223509089906", "227394831…
## $ category_id   <chr> "2268105426648170900", "2268105426648170900", "226810543…
## $ category_code <chr> "electronics.tablet", "electronics.tablet", "electronics…
## $ brand         <chr> "samsung", "samsung", "huawei", "huawei", "karcher", "ma…
## $ price         <dbl> 162.01, 162.01, 77.52, 77.52, 217.57, 39.33, 1387.01, 13…
## $ user_id       <chr> "1515915625441993984", "1515915625441993984", "151591562…

1.4 Initial Inspection

# Dimension of dataset
dim(df)
## [1] 2633521       8
# Structure and data types
str(df)
## spc_tbl_ [2,633,521 × 8] (S3: spec_tbl_df/tbl_df/tbl/data.frame)
##  $ event_time   : chr [1:2633521] "2020-04-24 11:50:39 UTC" "2020-04-24 11:50:39 UTC" "2020-04-24 14:37:43 UTC" "2020-04-24 14:37:43 UTC" ...
##  $ order_id     : chr [1:2633521] "2294359932054536986" "2294359932054536986" "2294444024058086220" "2294444024058086220" ...
##  $ product_id   : chr [1:2633521] "1515966223509089906" "1515966223509089906" "2273948319057183658" "2273948319057183658" ...
##  $ category_id  : chr [1:2633521] "2268105426648170900" "2268105426648170900" "2268105430162997728" "2268105430162997728" ...
##  $ category_code: chr [1:2633521] "electronics.tablet" "electronics.tablet" "electronics.audio.headphone" "electronics.audio.headphone" ...
##  $ brand        : chr [1:2633521] "samsung" "samsung" "huawei" "huawei" ...
##  $ price        : num [1:2633521] 162 162 77.5 77.5 217.6 ...
##  $ user_id      : chr [1:2633521] "1515915625441993984" "1515915625441993984" "1515915625447879434" "1515915625447879434" ...
##  - attr(*, "spec")=
##   .. cols(
##   ..   event_time = col_character(),
##   ..   order_id = col_character(),
##   ..   product_id = col_character(),
##   ..   category_id = col_character(),
##   ..   category_code = col_character(),
##   ..   brand = col_character(),
##   ..   price = col_double(),
##   ..   user_id = col_character()
##   .. )
##  - attr(*, "problems")=<externalptr>
# Quick preview
head(df)
# Column names
names(df)
## [1] "event_time"    "order_id"      "product_id"    "category_id"  
## [5] "category_code" "brand"         "price"         "user_id"

1.5 Check Missing Values

colSums(is.na(df))
##    event_time      order_id    product_id   category_id category_code 
##             0             0             0        431954        612202 
##         brand         price       user_id 
##        506005        431954       2069352
unclean_rows <- df %>%
  filter(if_any(everything(), is.na))

head(unclean_rows)
missing_percentage <- colSums(is.na(df)) / nrow(df) * 100
missing_percentage
##    event_time      order_id    product_id   category_id category_code 
##       0.00000       0.00000       0.00000      16.40215      23.24652 
##         brand         price       user_id 
##      19.21401      16.40215      78.57739

1.6 Check Duplicates

sum(duplicated(df))
## [1] 675
duplicate_rows <- df[duplicated(df), ]

head(duplicate_rows, 10)

Interpretation

The initial exploration reveals two data quality issues that must be addressed before analysis: missing values concentrated in identifier and descriptive columns (category_code, brand, user_id), and a number of fully duplicated rows. Both issues are handled in the cleaning stage below.


2.0 Data Cleaning

The cleaning process performs four operations: removing duplicate rows, converting event_time from a text string to a proper datetime object, converting category_id to character, and replacing missing values with sensible placeholders (“Unknown” for categorical fields, 0 for price).

df_cleaned <- df %>%
  # 1. Remove duplicate rows
  distinct() %>%

  # 2. Fix the event_time format to proper datetime
  mutate(event_time = ymd_hms(event_time)) %>%

  # 3. Change category_id to character
  mutate(category_id = as.character(category_id)) %>%

  # 4. Handle missing values accurately based on column types
  mutate(
    category_id   = ifelse(is.na(category_id), "Unknown", category_id),
    category_code = ifelse(is.na(category_code), "Unknown", category_code),
    brand         = ifelse(is.na(brand), "Unknown", brand),
    user_id       = ifelse(is.na(user_id), "Unknown", user_id),
    price         = ifelse(is.na(price), 0, price)
  )

# FINAL VERIFICATION CHECK
print("--- FINAL VERIFICATION CHECKS ---")
## [1] "--- FINAL VERIFICATION CHECKS ---"
print(paste("Remaining Duplicates:", sum(duplicated(df_cleaned))))
## [1] "Remaining Duplicates: 0"
print("Remaining NAs per column (Target is ALL ZEROS):")
## [1] "Remaining NAs per column (Target is ALL ZEROS):"
print(colSums(is.na(df_cleaned)))
##    event_time      order_id    product_id   category_id category_code 
##             0             0             0             0             0 
##         brand         price       user_id 
##             0             0             0
# Optional: save the cleaned dataset locally for reuse
write_csv(df_cleaned, "kz_cleaned.csv")

Interpretation

After cleaning, the dataset contains no duplicates and no missing values. Categorical gaps were filled with “Unknown” rather than dropped, preserving the full transaction volume for analysis. The event_time column is now a proper datetime, which enables the time-based feature engineering used later in the classification model.


3.0 Exploratory Data Analysis

3.1 Statistical Summary

Statistical summary was generated to understand the distribution and characteristics of each variable before further analysis.

# Summary
skim(df_cleaned)
Data summary
Name df_cleaned
Number of rows 2632846
Number of columns 8
_______________________
Column type frequency:
character 6
numeric 1
POSIXct 1
________________________
Group variables None

Variable type: character

skim_variable n_missing complete_rate min max empty n_unique whitespace
order_id 0 1 19 19 0 1435266 0
product_id 0 1 19 19 0 25113 0
category_id 0 1 7 19 0 928 0
category_code 0 1 4 38 0 511 0
brand 0 1 2 19 0 23022 0
user_id 0 1 7 19 0 233835 0

Variable type: numeric

skim_variable n_missing complete_rate mean sd p0 p25 p50 p75 p100 hist
price 0 1 128.81 228.44 0 4.61 34.7 161.78 50925.9 ▇▁▁▁▁

Variable type: POSIXct

skim_variable n_missing complete_rate min max median n_unique
event_time 0 1 1970-01-01 00:33:40 2020-11-21 10:10:30 2020-06-08 08:23:13 1316174
# Check key numeric variable
summary(df_cleaned$price)
##     Min.  1st Qu.   Median     Mean  3rd Qu.     Max. 
##     0.00     4.61    34.70   128.81   161.78 50925.90

3.2 Price Distribution

The distribution of product prices was examined to understand the spread of transaction values across the store.

# Drop non-positive (spending distribution of real transactions)
price_positive <- df_cleaned %>%
  filter(price > 0)

# Raw price scale
ggplot(price_positive, aes(x = price)) +
  geom_histogram(bins = 50, fill = "steelblue", color = "white") +
  labs(
    title = "Distribution of Product Prices",
    x = "Price",
    y = "Number of Transactions"
  )

# Log10 scale
ggplot(price_positive, aes(x = price)) +
  geom_histogram(bins = 50, fill = "steelblue", color = "white") +
  scale_x_log10() +
  labs(
    title = "Distribution of Product Prices (Log10 Scale)",
    x = "Price (log10)",
    y = "Number of Transactions"
  )

Interpretation

On the raw scale almost all transactions cluster near the low end with a long tail of expensive products. On the log scale the distribution is roughly bell-shaped, confirming that most purchases fall within a moderate price band while high-value purchases are comparatively rare. This pattern directly supports the high-value vs low-value classification target model.

3.3 Top Brands by Transaction Volume

The most frequently purchased brands were identified to understand which brands drive transaction volume.

# Count transactions per brand - 10 most frequent.
# Exclude "Unknown" brands
brand_freq <- df_cleaned %>%
  filter(brand != "Unknown") %>%
  count(brand, sort = TRUE) %>%
  head(10)

# reorder() sorts the bars by count; coord_flip() to keep the labels readable
ggplot(brand_freq, aes(x = reorder(brand, n), y = n)) +
  geom_col(fill = "darkorange") +
  coord_flip() +
  labs(
    title = "Top 10 Brands by Transaction Volume",
    x = "Brand",
    y = "Number of Transactions"
  )

Interpretation

A small group of brands accounts for a large share of all transactions. This concentration is why the modelling sections collapse the long tail of rare brands into an “Other” group and keep only the most frequent brands as predictors.

3.4 Top Product Categories by Transaction Volume

The most common product categories were examined to see where purchasing activity is concentrated.

# Count frequent product categories - 10 most frequent.
# Exclude "Unknown" categories
category_freq <- df_cleaned %>%
  filter(category_code != "Unknown") %>%
  count(category_code, sort = TRUE) %>%
  head(10)

ggplot(category_freq, aes(x = reorder(category_code, n), y = n)) +
  geom_col(fill = "darkorange") +
  coord_flip() +
  labs(
    title = "Top 10 Product Categories by Transaction Volume",
    x = "Category",
    y = "Number of Transactions"
  )

Interpretation

Purchasing activity is dominated by a handful of categories (largely electronics and accessories). The remaining categories each contribute only a small fraction of transactions. Hence, rare categories require grouping into “Other” before modelling.

3.5 Average Price by Category

Average prices were compared across the categories to see how product value differs by category.

# Average prices of known categories
avg_price_category <- df_cleaned %>%
  filter(category_code != "Unknown", price > 0) %>%
  group_by(category_code) %>%
  summarise(
    avg_price = mean(price),
    n_transactions = n()
  ) %>%
  arrange(desc(n_transactions)) %>%
  head(10)

# Sort highest-volume categories
ggplot(avg_price_category, aes(x = reorder(category_code, avg_price), y = avg_price)) +
  geom_col(fill = "seagreen") +
  coord_flip() +
  labs(
    title = "Average Price Among Top 10 Categories",
    x = "Category",
    y = "Average Price"
  )

Interpretation

Average price varies widely between categories: high-end electronics such as smartphones and notebooks sit far above accessories and consumables. This shows that category is a meaningful signal for price, suitable to be used as a predictor in both the classification and regression models.

3.6 Price Spread Across Top Categories

A boxplot was used to compare not just the average price but the full spread of prices within each major category.

# Top categories from the plot above
top_category_names <- avg_price_category$category_code

price_by_category <- df_cleaned %>%
  filter(category_code %in% top_category_names, price > 0)

# Log scale
ggplot(price_by_category, aes(x = category_code, y = price)) +
  geom_boxplot(fill = "lightblue") +
  scale_y_log10() +
  theme(axis.text.x = element_text(angle = 90, hjust = 1)) +
  labs(
    title = "Price Distribution Across Top Categories (Log10 Scale)",
    x = "Category",
    y = "Price (log10)"
  )

Interpretation

The price range varies across product categories. Some categories have similar prices, while others contain both low-priced and expensive products with many high outliers. This shows that category alone is not enough to accurately predict product price. Therefore, additional variables such as brand need to be included in the regression model to improve prediction accuracy.

3.7 Purchasing Patterns Over Time

Transaction timing was explored to reveal when customers are most active. These time-based patterns are used to engineer the temporal features.

# Drop any rows that failed to parse to avoid blank categories in the plots
time_features <- df_cleaned %>%
  filter(!is.na(event_time)) %>%
  mutate(
    hour    = hour(event_time),
    weekday = wday(event_time, label = TRUE, week_start = 1),
    month   = month(event_time, label = TRUE)
  )

# Transactions by hour of day
ggplot(time_features, aes(x = hour)) +
  geom_bar(fill = "purple") +
  labs(
    title = "Transactions by Hour of Day",
    x = "Hour (0-23)",
    y = "Number of Transactions"
  )

# Transactions by weekday
ggplot(time_features, aes(x = weekday)) +
  geom_bar(fill = "purple") +
  labs(
    title = "Transactions by Weekday",
    x = "Weekday",
    y = "Number of Transactions"
  )

# Transactions by month
ggplot(time_features, aes(x = month)) +
  geom_bar(fill = "purple") +
  labs(
    title = "Transactions by Month",
    x = "Month",
    y = "Number of Transactions"
  )

Interpretation

Purchases are not spread evenly across time: activity rises and falls across the hours of the day and differs between weekdays and months. Because these patterns are clear, hour, weekday and month can be engineered as features for the classification model.

3.8 EDA Summary

The exploratory analysis produced several findings that shape the modelling work that follows:

  1. Price is strongly right-skewed, with most transactions at low values and a small number of high-value purchases. This supports the high-value vs low-value target created in Section 4.0.
  2. Brands and categories are highly concentrated, where a few brands and categories account for most transactions. This justifies grouping rare levels into an “Other” category before modelling.
  3. Category and brand are clearly linked to price, both in average level and in spread, making them useful predictors for the regression model in Section 5.0.
  4. Purchasing activity varies by hour, weekday and month, which motivates the time-based features used in the classification model.

4.0 Classification Modelling

4.1 Take Sample Data

A sample is drawn to reduce computation time. The original df is preserved; the sample is stored in df_class for the classification work.

set.seed(123)

df_class <- df_cleaned %>% sample_n(50000)

Interpretation

The dataset was reduced to 50,000 rows, which ensures faster computation and efficiency while still keeping a large enough sample to be representative.

4.2 Feature Engineering

df_class$hour <- as.factor(format(df_class$event_time, "%H"))

df_class$weekday <- as.factor(weekdays(df_class$event_time))

df_class$month <- as.factor(format(df_class$event_time, "%m"))

Interpretation

Time-based features may reveal purchase behaviour patterns, such as high-value purchases being more common at certain hours or days.

4.3 Create Target Variable

# High-Value vs Low-Value Purchase
threshold <- quantile(df_class$price, 0.75)
threshold
##    75% 
## 157.15
df_class$purchase_class <- ifelse(
  df_class$price >= threshold,
  "High",
  "Low"
)

df_class$purchase_class <- as.factor(df_class$purchase_class)

table(df_class$purchase_class)
## 
##  High   Low 
## 12503 37497

Interpretation

To accurately predict customer behaviour and isolate high-value revenue drivers, a binary target classification variable (purchase_class) was engineered from the continuous price metric. Following an exploratory baseline audit of the price distribution, a strict mathematical threshold was established at the 75th percentile (3rd quartile).

Any transaction containing an item priced at or above the threshold was categorised as “High” (representing the premium top-tier quadrant of sales), while items priced under the threshold were flagged as “Low”.

The resulting distribution shows roughly 12,500 high-value vs 37,500 low-value purchases, indicating a moderately imbalanced dataset suitable for classification modelling.

4.4 Keep Top 20 Brands/Categories

# Top brands
top_brands <- names(
  sort(table(df_class$brand), decreasing = TRUE)
)[1:20]

df_class$brand <- ifelse(
  df_class$brand %in% top_brands,
  df_class$brand,
  "Other"
)

# Top categories
top_categories <- names(
  sort(table(df_class$category_code), decreasing = TRUE)
)[1:20]

df_class$category_code <- ifelse(
  df_class$category_code %in% top_categories,
  df_class$category_code,
  "Other"
)

# Convert to factor
df_class$brand <- as.factor(df_class$brand)
df_class$category_code <- as.factor(df_class$category_code)

Interpretation

This reduces noise and avoids sparse categories, making the model more efficient and focused on the most common brands/categories.

4.5 Train/Test Split

# Select variables
model_df <- df_class %>%
  select(
    purchase_class,
    brand,
    category_code,
    hour,
    weekday,
    month
  )

# Train/Test Split (80:20)
set.seed(123)

trainIndex <- createDataPartition(
  model_df$purchase_class,
  p = 0.80,
  list = FALSE
)

data_train <- model_df[trainIndex, ]
data_test  <- model_df[-trainIndex, ]

4.6 Cross Validation

# Repeated CV, 5 folds
ctrl <- trainControl(
  method = "repeatedcv",
  number = 5,
  classProbs = TRUE,
  summaryFunction = twoClassSummary
)

Interpretation

  • Repeated cross-validation with class probabilities and ROC metrics was set up.
  • This provides a more reliable estimate of model performance by testing across multiple folds, and using ROC/AUC ensures evaluation remains sound even with imbalanced classes.

4.7 Logistic Regression Model

model_log <- train(
  purchase_class ~ .,
  data = data_train,
  method = "glm",
  family = "binomial",
  metric = "ROC",
  trControl = ctrl
)

# Display model
print(model_log)
## Generalized Linear Model 
## 
## 40001 samples
##     5 predictor
##     2 classes: 'High', 'Low' 
## 
## No pre-processing
## Resampling: Cross-Validated (5 fold, repeated 1 times) 
## Summary of sample sizes: 32002, 32001, 32000, 32001, 32000 
## Resampling results:
## 
##   ROC        Sens       Spec     
##   0.9123125  0.7338785  0.9108608

Interpretation

  • ROC ≈ 0.912 → The model has excellent ability to distinguish between High vs Low value purchases.
  • Sensitivity ≈ 0.734 → About 73% of high-value purchases were correctly identified.
  • Specificity ≈ 0.911 → About 91% of low-value purchases were correctly identified.
  • The model is strong overall, but slightly better at identifying low-value purchases than high-value ones.

4.8 Naive Bayes Model

model_nb <- train(
  purchase_class ~ .,
  data = data_train,
  method = "nb",
  metric = "ROC",
  trControl = ctrl
)

# Display model
print(model_nb)
## Naive Bayes 
## 
## 40001 samples
##     5 predictor
##     2 classes: 'High', 'Low' 
## 
## No pre-processing
## Resampling: Cross-Validated (5 fold, repeated 1 times) 
## Summary of sample sizes: 32000, 32000, 32001, 32001, 32002 
## Resampling results across tuning parameters:
## 
##   usekernel  ROC        Sens  Spec
##   FALSE            NaN  NaN   NaN 
##    TRUE      0.8930407    0     1 
## 
## Tuning parameter 'fL' was held constant at a value of 0
## Tuning
##  parameter 'adjust' was held constant at a value of 1
## ROC was used to select the optimal model using the largest value.
## The final values used for the model were fL = 0, usekernel = TRUE and adjust
##  = 1.

Interpretation

  • ROC ≈ 0.893 → Slightly lower than logistic regression (0.912), but still strong discrimination between High vs Low purchases.
  • Sensitivity ≈ 0 → The model failed to correctly identify any high-value purchases.
  • Specificity ≈ 1 → The model perfectly identified low-value purchases.
  • The model is biased toward predicting “Low” purchases only, which makes it unsuitable for detecting high-value customers.

4.9 Random Forest Model

model_rf <- train(
  purchase_class ~ .,
  data = data_train,
  method = "rf",
  metric = "ROC",
  trControl = ctrl,
  ntree = 50
)

# Display model
print(model_rf)
## Random Forest 
## 
## 40001 samples
##     5 predictor
##     2 classes: 'High', 'Low' 
## 
## No pre-processing
## Resampling: Cross-Validated (5 fold, repeated 1 times) 
## Summary of sample sizes: 32000, 32000, 32001, 32002, 32001 
## Resampling results across tuning parameters:
## 
##   mtry  ROC        Sens       Spec     
##    2    0.8639198  0.4686595  0.9474966
##   40    0.8937572  0.6827948  0.9171948
##   79    0.8888142  0.6803948  0.9103943
## 
## ROC was used to select the optimal model using the largest value.
## The final value used for the model was mtry = 40.

Interpretation

  • ROC ≈ 0.893 (best at mtry = 40) → Very good discrimination between High vs Low purchases, slightly lower than Logistic Regression (0.912) but stronger than Naive Bayes (0.893 with poor sensitivity).
  • Sensitivity ≈ 0.683 → About 68% of high-value purchases correctly identified.
  • Specificity ≈ 0.917 → About 92% of low-value purchases correctly identified.
  • Random Forest balances both classes better than Naive Bayes, and handles categorical predictors more gracefully than Logistic Regression.

4.10 Model Predictions

pred_log <- predict(model_log, data_test)
pred_nb  <- predict(model_nb, data_test)
pred_rf  <- predict(model_rf, data_test)

4.11 Confusion Matrices

Logistic Regression

cm_log <- confusionMatrix(pred_log, data_test$purchase_class)
cm_log
## Confusion Matrix and Statistics
## 
##           Reference
## Prediction High  Low
##       High 1880  678
##       Low   620 6821
##                                           
##                Accuracy : 0.8702          
##                  95% CI : (0.8634, 0.8767)
##     No Information Rate : 0.75            
##     P-Value [Acc > NIR] : <2e-16          
##                                           
##                   Kappa : 0.6565          
##                                           
##  Mcnemar's Test P-Value : 0.1136          
##                                           
##             Sensitivity : 0.7520          
##             Specificity : 0.9096          
##          Pos Pred Value : 0.7349          
##          Neg Pred Value : 0.9167          
##              Prevalence : 0.2500          
##          Detection Rate : 0.1880          
##    Detection Prevalence : 0.2558          
##       Balanced Accuracy : 0.8308          
##                                           
##        'Positive' Class : High            
## 

Naive Bayes

cm_nb <- confusionMatrix(pred_nb, data_test$purchase_class)
cm_nb
## Confusion Matrix and Statistics
## 
##           Reference
## Prediction High  Low
##       High    0    0
##       Low  2500 7499
##                                           
##                Accuracy : 0.75            
##                  95% CI : (0.7414, 0.7584)
##     No Information Rate : 0.75            
##     P-Value [Acc > NIR] : 0.5054          
##                                           
##                   Kappa : 0               
##                                           
##  Mcnemar's Test P-Value : <2e-16          
##                                           
##             Sensitivity : 0.00            
##             Specificity : 1.00            
##          Pos Pred Value :  NaN            
##          Neg Pred Value : 0.75            
##              Prevalence : 0.25            
##          Detection Rate : 0.00            
##    Detection Prevalence : 0.00            
##       Balanced Accuracy : 0.50            
##                                           
##        'Positive' Class : High            
## 

Random Forest

cm_rf <- confusionMatrix(pred_rf, data_test$purchase_class)
cm_rf
## Confusion Matrix and Statistics
## 
##           Reference
## Prediction High  Low
##       High 1654  536
##       Low   846 6963
##                                           
##                Accuracy : 0.8618          
##                  95% CI : (0.8549, 0.8685)
##     No Information Rate : 0.75            
##     P-Value [Acc > NIR] : < 2.2e-16       
##                                           
##                   Kappa : 0.6156          
##                                           
##  Mcnemar's Test P-Value : < 2.2e-16       
##                                           
##             Sensitivity : 0.6616          
##             Specificity : 0.9285          
##          Pos Pred Value : 0.7553          
##          Neg Pred Value : 0.8917          
##              Prevalence : 0.2500          
##          Detection Rate : 0.1654          
##    Detection Prevalence : 0.2190          
##       Balanced Accuracy : 0.7951          
##                                           
##        'Positive' Class : High            
## 

Interpretation

  • Logistic Regression is balanced and reliable, slightly favouring low-value detection but still strong for high-value. Naive Bayes collapsed: it only predicts “Low” and is unusable for identifying high-value customers. Random Forest is dependable, slightly less sensitive than Logistic Regression but very strong in specificity.
  • Logistic Regression is the best overall model here, with Random Forest as a strong alternative. Naive Bayes is not suitable for this dataset.

4.12 ROC Curve and AUC

# Compare Logistic Regression vs Random Forest
# Logistic Regression probabilities
log_probs <- predict(model_log, data_test, type = "prob")

# Random Forest probabilities
rf_probs <- predict(model_rf, data_test, type = "prob")

# ROC for Logistic Regression
roc_log <- roc(
  response = data_test$purchase_class,
  predictor = log_probs$High
)

# ROC for Random Forest
roc_rf <- roc(
  response = data_test$purchase_class,
  predictor = rf_probs$High
)

# Plot Logistic Regression ROC
plot(roc_log, col = "blue", main = "ROC Curve Comparison")

# Add Random Forest ROC
plot(roc_rf, col = "red", add = TRUE)

# Add legend
legend(
  "bottomright",
  legend = c("Logistic Regression", "Random Forest"),
  col = c("blue", "red"),
  lwd = 2
)

# AUC values
auc_log <- auc(roc_log)
auc_rf  <- auc(roc_rf)

data.frame(
  Model = c("Logistic Regression", "Random Forest"),
  AUC   = round(c(auc_log, auc_rf), 3)
)

Interpretation

  • Both models perform well above random guessing (AUC > 0.5).
  • Logistic Regression edges out Random Forest in overall discrimination (higher AUC).
  • Random Forest is more flexible with categorical features and still competitive.
  • The ROC curves lying above the diagonal line confirm both models are useful classifiers.

4.13 Feature Importance

importance_rf <- varImp(model_rf)
importance_rf
## rf variable importance
## 
##   only 20 most important variables shown (out of 79)
## 
##                                               Overall
## category_codeelectronics.smartphone            100.00
## category_codeappliances.kitchen.refrigerators   74.57
## category_codeelectronics.video.tv               52.44
## brandapple                                      50.12
## category_codecomputers.notebook                 45.55
## category_codeappliances.kitchen.washer          44.86
## brandlg                                         41.29
## brandUnknown                                    35.14
## brandbeko                                       33.46
## brandsamsung                                    30.40
## category_codeUnknown                            30.18
## brandOther                                      29.92
## brandbosch                                      21.22
## category_codeappliances.kitchen.hood            16.81
## weekdayTuesday                                  15.28
## weekdaySunday                                   14.48
## weekdayWednesday                                14.35
## weekdaySaturday                                 14.23
## weekdayThursday                                 14.15
## category_codeOther                              13.49
plot(importance_rf, top = 15, main = "Top 15 Features - Random Forest")

Interpretation

  • category_code dominates → Product type is the strongest signal of high vs low purchase value.
  • Brand matters → Premium brands (Apple, LG, Samsung) are more likely associated with high-value purchases.
  • Temporal features (weekday, month) have smaller but non-negligible influence, suggesting purchase behaviour varies by time.

Marketing strategies should prioritise product categories and premium brands, while also considering timing patterns.

4.14 Model Comparison

results <- resamples(
  list(
    Logistic_Regression = model_log,
    Naive_Bayes = model_nb,
    Random_Forest = model_rf
  )
)

# Summary statistics
summary(results)
## 
## Call:
## summary.resamples(object = results)
## 
## Models: Logistic_Regression, Naive_Bayes, Random_Forest 
## Number of resamples: 5 
## 
## ROC 
##                          Min.   1st Qu.    Median      Mean   3rd Qu.      Max.
## Logistic_Regression 0.9105447 0.9111047 0.9129353 0.9123125 0.9129665 0.9140114
## Naive_Bayes         0.8885272 0.8918082 0.8937953 0.8930407 0.8938679 0.8972051
## Random_Forest       0.8872343 0.8877338 0.8940993 0.8937572 0.8967984 0.9029202
##                     NA's
## Logistic_Regression    0
## Naive_Bayes            0
## Random_Forest          0
## 
## Sens 
##                          Min. 1st Qu.    Median      Mean   3rd Qu.      Max.
## Logistic_Regression 0.7245000  0.7300 0.7321339 0.7338785 0.7321339 0.7506247
## Naive_Bayes         0.0000000  0.0000 0.0000000 0.0000000 0.0000000 0.0000000
## Random_Forest       0.6676662  0.6775 0.6801599 0.6827948 0.6845000 0.7041479
##                     NA's
## Logistic_Regression    0
## Naive_Bayes            0
## Random_Forest          0
## 
## Spec 
##                          Min.   1st Qu.    Median      Mean   3rd Qu.      Max.
## Logistic_Regression 0.9065000 0.9071667 0.9111519 0.9108608 0.9131522 0.9163333
## Naive_Bayes         1.0000000 1.0000000 1.0000000 1.0000000 1.0000000 1.0000000
## Random_Forest       0.9116667 0.9131667 0.9171667 0.9171948 0.9196533 0.9243207
##                     NA's
## Logistic_Regression    0
## Naive_Bayes            0
## Random_Forest          0
# Boxplot comparison
bwplot(results)

Interpretation

  • ROC → Logistic > RF > NB
  • Sensitivity → Logistic > RF > NB
  • Specificity → RF > Logistic > NB

4.15 Classification Modelling Summary

Logistic Regression is the best overall model, Random Forest is a dependable backup, and Naive Bayes is discarded. Insights show that product type and brand are the key factors influencing high-value purchases.


5.0 Regression Modelling

5.1 Preview Cleaned Dataset

The regression section reuses the cleaned dataset from Section 2.0.

head(df_cleaned)

5.2 Data Preparation

5.2.1 Sampling the Dataset

A sample of 150,000 observations was selected to improve computational efficiency during regression modelling.

set.seed(123)

df_sample <- df_cleaned %>%
  sample_n(150000)

dim(df_sample)
## [1] 150000      8

5.2.2 Filtering Valid Brand Values

Invalid or non-meaningful brand values were removed to improve model quality.

df_sample <- df_sample %>%
  filter(grepl("[A-Za-z]", brand))

dim(df_sample)
## [1] 147838      8

Interpretation

The dataset was filtered to retain only records with valid alphabetic brand values. A small number of records with invalid or non-meaningful brand entries were removed to improve the quality of the regression analysis.

5.2.3 Factor Conversion

Categorical variables are converted into factor format for regression modelling.

df_sample$brand <- factor(df_sample$brand)
df_sample$category_code <- factor(df_sample$category_code)

str(df_sample[, c("brand", "category_code")])
## tibble [147,838 × 2] (S3: tbl_df/tbl/data.frame)
##  $ brand        : Factor w/ 605 levels "a-case","accesstyle",..: 251 560 500 82 560 29 91 529 500 137 ...
##  $ category_code: Factor w/ 297 levels "0.00","0.05",..: 267 99 183 209 99 267 202 192 183 236 ...

Interpretation

Categorical variables were converted to factor format so that they can be correctly handled by the regression model when estimating the relationship between product characteristics and price.

5.2.4 Price Distribution by Brand

A boxplot visualisation was created to compare price distributions across brands.

top_brands_reg <- names(
  sort(table(df_sample$brand), decreasing = TRUE)
)[1:20]

brand_plot <- df_sample %>%
  filter(brand %in% top_brands_reg)

ggplot(
  brand_plot,
  aes(x = reorder(brand, price, median), y = price)
) +
  geom_boxplot(fill = "skyblue") +
  coord_flip() +
  labs(
    title = "Price Distribution by Top 20 Brands",
    x = "Brand",
    y = "Price"
  )

Interpretation

The boxplot shows that product prices vary considerably across the top 20 brands. Some brands have higher median prices and a wider spread of prices, while others have lower and more consistent price ranges. Several brands also exhibit extreme high-price outliers, indicating the presence of premium products. These differences suggest that brand has a significant influence on product price and is therefore an important predictor to include in the regression model.

5.3 Train-Test Split

set.seed(123)

train_index <- createDataPartition(
  y = df_sample$price,
  p = 0.80,
  list = FALSE
)

train_data <- df_sample[train_index, ]
test_data  <- df_sample[-train_index, ]

dim(train_data)
## [1] 118272      8
dim(test_data)
## [1] 29566     8
# Ensure train and test use the same factor levels

train_data$brand <- factor(train_data$brand)
train_data$category_code <- factor(train_data$category_code)

test_data$brand <- factor(
  test_data$brand,
  levels = levels(train_data$brand)
)

test_data$category_code <- factor(
  test_data$category_code,
  levels = levels(train_data$category_code)
)

Interpretation

The sampled dataset was divided into 80% training data and 20% testing data. The training dataset is used to build the regression model, while the testing dataset is used to evaluate its predictive performance on unseen data. Aligning factor levels between the two sets prevents prediction errors when the test set contains brand or category levels absent from training.

5.4 Simple Linear Regression

simple_model <- lm(
  price ~ brand,
  data = train_data
)

summary(simple_model)
## 
## Call:
## lm(formula = price ~ brand, data = train_data)
## 
## Residuals:
##    Min     1Q Median     3Q    Max 
## -706.8  -38.6  -11.7    5.8 5341.7 
## 
## Coefficients:
##                         Estimate Std. Error t value Pr(>|t|)    
## (Intercept)              2.70629   19.39700   0.140 0.889039    
## brandaccesstyle         28.02514   64.33257   0.436 0.663107    
## brandaction             22.73371  163.44203   0.139 0.889377    
## brandadidas             39.40371  116.38201   0.339 0.734933    
## brandadvantek           11.67260   31.00825   0.376 0.706594    
## brandaeg               634.61871   69.03443   9.193  < 2e-16 ***
## brandaerocool          114.86159   30.60403   3.753 0.000175 ***
## brandaimoto             53.40696   32.16629   1.660 0.096849 .  
## brandairline             8.97121   31.22200   0.287 0.773855    
## brandakku               65.90621   83.42966   0.790 0.429552    
## brandaksion             40.23315   22.15294   1.816 0.069349 .  
## brandakvafor             6.63411   19.98774   0.332 0.739958    
## brandalex               67.64371  163.44203   0.414 0.678970    
## brandalfa                7.45371  163.44203   0.046 0.963625    
## brandalienware        3617.64371  163.44203  22.134  < 2e-16 ***
## brandalmatv             20.42371  116.38201   0.175 0.860696    
## brandaltair             34.30371  163.44203   0.210 0.833759    
## brandaltel              44.78843   22.89552   1.956 0.050443 .  
## brandaltex             146.65371   46.17410   3.176 0.001493 ** 
## brandamazon            177.24621   83.42966   2.124 0.033631 *  
## brandamd               207.24493   34.26859   6.048 1.47e-09 ***
## brandamigami            -0.41629   42.88838  -0.010 0.992256    
## brandanymode            20.42371   28.68160   0.712 0.476414    
## brandaoc               169.50887   25.45112   6.660 2.75e-11 ***
## brandaoki              119.06756   49.01195   2.429 0.015127 *  
## brandapc                21.92471   54.86300   0.400 0.689432    
## brandapollo              4.33590   24.44511   0.177 0.859216    
## brandapple             625.75330   19.59302  31.938  < 2e-16 ***
## brandaqua               32.58064   49.01195   0.665 0.506212    
## brandaquadent           53.47371   57.46811   0.930 0.352117    
## brandaquael             35.46371  163.44203   0.217 0.828224    
## brandaquapick           78.29371   49.01195   1.597 0.110170    
## brandarena              17.87371  163.44203   0.109 0.912919    
## brandariston           125.76252   21.19911   5.932 2.99e-09 ***
## brandarktika            39.37121   60.56712   0.650 0.515666    
## brandarnica             58.15371   95.68313   0.608 0.543339    
## brandart.fit            67.33371   50.70501   1.328 0.184197    
## brandartberry           -0.50629  163.44203  -0.003 0.997528    
## brandartel             130.24371   52.63574   2.474 0.013346 *  
## brandasrock             70.92838   46.17410   1.536 0.124515    
## brandastonish           13.86371   95.68313   0.145 0.884796    
## brandasus              521.30530   20.06904  25.976  < 2e-16 ***
## brandatlant            331.32402   23.99514  13.808  < 2e-16 ***
## brandatmor              40.67205   50.70501   0.802 0.422479    
## brandatom               20.42371  163.44203   0.125 0.900555    
## brandaudac              20.42371  163.44203   0.125 0.900555    
## brandaura               -2.54629  116.38201  -0.022 0.982545    
## brandausini              6.70518   23.87255   0.281 0.778807    
## brandauthor            219.26371  163.44203   1.342 0.179748    
## brandava                69.16877   19.52320   3.543 0.000396 ***
## brandavermedia         149.27705   95.68313   1.560 0.118735    
## brandavrora             -1.03548   28.30256  -0.037 0.970815    
## brandawax                2.85371   21.07422   0.135 0.892286    
## brandawei               20.04418   31.44413   0.637 0.523831    
## brandbaboo              10.42371  116.38201   0.090 0.928633    
## brandbabyliss           47.85437   25.73939   1.859 0.063003 .  
## brandbaltextile         99.00371  116.38201   0.851 0.394949    
## brandbarbie             18.10371   95.68313   0.189 0.849933    
## brandbardahl            21.34371  163.44203   0.131 0.896101    
## brandbarjher             3.79381   20.91293   0.181 0.856046    
## brandbarkan             34.40887   21.85269   1.575 0.115355    
## brandbeats             192.70514   64.33257   2.995 0.002741 ** 
## brandbeeline            38.70371   25.62079   1.511 0.130884    
## brandbeko              262.39340   19.86032  13.212  < 2e-16 ***
## brandbelcando           77.43371  163.44203   0.474 0.635666    
## brandbelita              0.88371   95.68313   0.009 0.992631    
## brandbelitam             0.37371  163.44203   0.002 0.998176    
## brandbellissima         41.57355   28.42532   1.463 0.143592    
## brandbequiet            60.86371   83.42966   0.730 0.465684    
## brandberghoff           12.89333   20.87011   0.618 0.536715    
## brandberkley             2.59371  163.44203   0.016 0.987339    
## brandberry              34.30371  163.44203   0.210 0.833759    
## brandbestway            21.31816   57.46811   0.371 0.710671    
## brandbeurer             35.21816   24.52237   1.436 0.150958    
## brandbfgoodrich         53.52371  163.44203   0.327 0.743307    
## brandbioderma           21.60371  163.44203   0.132 0.894842    
## brandbiol                3.32502   39.00427   0.085 0.932065    
## brandbiolane             4.23371  163.44203   0.026 0.979334    
## brandbiostar            47.26705   95.68313   0.494 0.621310    
## brandbirjusa           274.48065   21.84381  12.566  < 2e-16 ***
## brandbisfree             0.97371  163.44203   0.006 0.995247    
## brandblackstar          80.60371  116.38201   0.693 0.488575    
## brandblehk              28.08371  163.44203   0.172 0.863574    
## brandbloody             23.20644   21.43802   1.082 0.279037    
## brandbona               77.36271   35.41392   2.185 0.028925 *  
## brandborasco            -1.92329   41.14725  -0.047 0.962719    
## brandbork              316.50962   24.15827  13.102  < 2e-16 ***
## brandborner             55.14371   75.12426   0.734 0.462930    
## brandbosch             316.70935   19.82988  15.971  < 2e-16 ***
## brandbose              311.04496   60.56712   5.136 2.82e-07 ***
## brandbradex              9.04091   37.81172   0.239 0.811026    
## brandbrateck           136.16371  163.44203   0.833 0.404789    
## brandbraun              88.65643   20.07917   4.415 1.01e-05 ***
## brandbrelil              8.15371  163.44203   0.050 0.960212    
## brandbridgestone        94.57038   95.68313   0.988 0.322973    
## brandbrother           460.23371   69.03443   6.667 2.63e-11 ***
## brandbruder             53.29371  163.44203   0.326 0.744371    
## brandbuebchen            1.92371  163.44203   0.012 0.990609    
## brandbuff               20.88371  163.44203   0.128 0.898328    
## brandbushido             8.14716   35.83878   0.227 0.820169    
## brandbyintek           321.34371  163.44203   1.966 0.049289 *  
## brandbykski              1.69371   57.46811   0.029 0.976488    
## brandcablexpert         -1.80629  116.38201  -0.016 0.987617    
## brandcalgon              4.91371  163.44203   0.030 0.976016    
## brandcamelion           -0.38478   20.25732  -0.019 0.984845    
## brandcannondale       1038.70371  163.44203   6.355 2.09e-10 ***
## brandcanon             158.57455   21.81754   7.268 3.67e-13 ***
## brandcanyon             95.26705   69.03443   1.380 0.167591    
## brandcasada            575.97371  163.44203   3.524 0.000425 ***
## brandcasio             213.58871  116.38201   1.835 0.066473 .  
## brandcaso              549.88099   52.63574  10.447  < 2e-16 ***
## brandcaspio             89.86371   64.33257   1.397 0.162458    
## brandcatrice            -0.63629  163.44203  -0.004 0.996894    
## brandcdc                 7.38671   54.86300   0.135 0.892897    
## brandcelebrat           -2.47629  163.44203  -0.015 0.987912    
## brandchicco             19.73417   39.66589   0.498 0.618830    
## brandchina               5.26669   23.30094   0.226 0.821179    
## brandcilek             546.67847   23.67317  23.093  < 2e-16 ***
## brandcliny               0.62371  163.44203   0.004 0.996955    
## brandcollecta            0.51371  116.38201   0.004 0.996478    
## brandcolorful           42.57735   52.63574   0.809 0.418571    
## brandcompliment          0.83231   30.04970   0.028 0.977903    
## brandcontinent          23.43475   24.99413   0.938 0.348447    
## brandcontinental       147.96371  116.38201   1.271 0.203602    
## brandcoolinar           10.38571   24.05902   0.432 0.665977    
## brandcort              227.36371  163.44203   1.391 0.164199    
## brandcougar            100.52657   47.51275   2.116 0.034366 *  
## brandcremesso            8.00352   29.71070   0.269 0.787636    
## brandcullmann           46.21157   47.51275   0.973 0.330747    
## brandcyberpower          3.05371  163.44203   0.019 0.985093    
## brandd-color            13.47371  163.44203   0.082 0.934299    
## brandd-link             13.81850   39.00427   0.354 0.723128    
## branddaewoo            440.85705   69.03443   6.386 1.71e-10 ***
## branddaikin            575.97371  163.44203   3.524 0.000425 ***
## branddaiwa              38.70371  163.44203   0.237 0.812809    
## branddam                -2.03629  163.44203  -0.012 0.990060    
## branddarina            188.08705   95.68313   1.966 0.049332 *  
## branddc-girls            6.53371   50.70501   0.129 0.897471    
## branddecoroom           41.36371  163.44203   0.253 0.800208    
## branddeepcool           21.31235   25.99093   0.820 0.412222    
## branddeerma             36.62371  116.38201   0.315 0.753001    
## branddefender           20.42371   69.03443   0.296 0.767347    
## branddell              585.54305   46.17410  12.681  < 2e-16 ***
## branddelonghi          239.64988   21.27921  11.262  < 2e-16 ***
## branddelux               7.23630   21.06596   0.344 0.731218    
## branddeluxe             33.67093   20.45441   1.646 0.099737 .  
## branddemidovskiy         9.53064   49.01195   0.194 0.845820    
## branddepileve            1.86371  163.44203   0.011 0.990902    
## branddermal             -1.77629   95.68313  -0.019 0.985189    
## branddermoviva           0.65371   33.28406   0.020 0.984330    
## branddesignskin         -0.82829   75.12426  -0.011 0.991203    
## branddifferent          39.92922   22.41112   1.782 0.074806 .  
## branddji               433.99022   26.33548  16.479  < 2e-16 ***
## branddogland            31.93821   21.56896   1.481 0.138676    
## branddomini             96.03371   95.68313   1.004 0.315543    
## branddougez             -0.50629  163.44203  -0.003 0.997528    
## branddr.beckmann        -0.41629   57.46811  -0.007 0.994220    
## brandduracell            0.77240   25.34314   0.030 0.975686    
## branddxracer           281.95856   34.26859   8.228  < 2e-16 ***
## branddyson             551.54969   27.24034  20.248  < 2e-16 ***
## brande.gov              11.16371   31.67517   0.352 0.724506    
## brandecocool            59.76952   35.01180   1.707 0.087801 .  
## brandecologystone       64.32371   83.42966   0.771 0.440712    
## brandedifier            12.21149   42.88838   0.285 0.775854    
## brandeglo               25.06705   95.68313   0.262 0.793337    
## brandegoiste            -0.41629   83.42966  -0.005 0.996019    
## brandehlektrostandart   22.73371  163.44203   0.139 0.889377    
## brandehra                1.00105   31.00825   0.032 0.974246    
## brandelari              41.36059   28.06706   1.474 0.140583    
## brandelectrolux        397.21067   20.49550  19.380  < 2e-16 ***
## brandemsa               32.63071   41.14725   0.793 0.427766    
## brandenergea            23.32848   40.37808   0.578 0.563433    
## brandepson              72.10544   20.94406   3.443 0.000576 ***
## brandergolux            -0.60616   23.30094  -0.026 0.979246    
## brandeset               13.97356   22.62745   0.618 0.536874    
## brandetalon            103.75371  163.44203   0.635 0.525557    
## brandeuroprint          13.98571   75.12426   0.186 0.852314    
## brandeverlast           57.45371  163.44203   0.352 0.725196    
## brandeyfel               1.90371  163.44203   0.012 0.990707    
## brandezviz              50.74371   83.42966   0.608 0.543042    
## brandfender            413.70371  163.44203   2.531 0.011369 *  
## brandfiltero             3.16552   26.33548   0.120 0.904325    
## brandfissman            11.57348   21.89809   0.529 0.597143    
## brandfitokosmetik       -1.68629  163.44203  -0.010 0.991768    
## brandfixsen             12.92371  163.44203   0.079 0.936975    
## brandfizan              13.24371  163.44203   0.081 0.935418    
## brandflama             131.13096   35.83878   3.659 0.000253 ***
## brandfly                29.67371   95.68313   0.310 0.756467    
## brandforward           194.03371  163.44203   1.187 0.235162    
## brandfossil            117.86826   52.63574   2.239 0.025137 *  
## brandfranke            117.80705   95.68313   1.231 0.218243    
## brandfujifilm          274.31625   28.18319   9.733  < 2e-16 ***
## brandgalaxy             11.93038   95.68313   0.125 0.900772    
## brandgamdias           179.14943   64.33257   2.785 0.005358 ** 
## brandgamemax            47.72731   26.97044   1.770 0.076794 .  
## brandgarmin            725.87201   31.91568  22.743  < 2e-16 ***
## brandgefest            278.00538   29.39331   9.458  < 2e-16 ***
## brandgembird            22.73371  163.44203   0.139 0.889377    
## brandgenau             339.39871  116.38201   2.916 0.003543 ** 
## brandgeneris           101.43371  163.44203   0.621 0.534858    
## brandgenius             10.76355   20.58809   0.523 0.601111    
## brandgerat               5.68390   29.39331   0.193 0.846666    
## brandgewa               44.08871   83.42966   0.528 0.597185    
## brandgeyzer              1.87371   60.56712   0.031 0.975321    
## brandgezatone           43.69064   27.95405   1.563 0.118068    
## brandggg                17.93736   21.87065   0.820 0.412128    
## brandgiant             547.96871  116.38201   4.708 2.50e-06 ***
## brandgigabyte          240.01371   28.18319   8.516  < 2e-16 ***
## brandgillette            5.66371   83.42966   0.068 0.945876    
## brandgiottos            66.71371  163.44203   0.408 0.683143    
## brandglasslock           7.16371   27.73687   0.258 0.796196    
## brandglassware          15.12858   27.24034   0.555 0.578640    
## brandglobal              3.05674   34.26859   0.089 0.928923    
## brandgo-sport          778.52371  163.44203   4.763 1.91e-06 ***
## brandgolf               -1.54629  163.44203  -0.009 0.992452    
## brandgoodride           46.11371   21.27921   2.167 0.030231 *  
## brandgoodyear           48.19871   60.56712   0.796 0.426156    
## brandgopro             160.28129   34.26859   4.677 2.91e-06 ***
## brandgorenje           308.23955   21.14337  14.579  < 2e-16 ***
## brandgrans              30.74205   28.55161   1.077 0.281608    
## brandgreenway          212.50059   30.41270   6.987 2.82e-12 ***
## brandgrillver           62.08371  163.44203   0.380 0.704056    
## brandgrohe             160.32706   20.19369   7.939 2.05e-15 ***
## brandgtec               -1.43545   50.70501  -0.028 0.977415    
## brandgutrend           282.05538   42.88838   6.576 4.84e-11 ***
## brandhabilead           45.65371   23.84292   1.915 0.055524 .  
## brandhansa             292.85768   20.72577  14.130  < 2e-16 ***
## brandhaushalt           37.54971   33.59659   1.118 0.263713    
## brandhenkel              4.64038   69.03443   0.067 0.946408    
## brandherschel           75.62871  116.38201   0.650 0.515802    
## brandhintek             54.59705   95.68313   0.571 0.568270    
## brandhitachi          2180.14371  116.38201  18.733  < 2e-16 ***
## brandhms               275.04371  163.44203   1.683 0.092412 .  
## brandhoco               -1.47429   37.81172  -0.039 0.968898    
## brandhonor             113.27003   20.52848   5.518 3.44e-08 ***
## brandhotpoint-ariston  305.08151   21.37253  14.274  < 2e-16 ***
## brandhp                297.93821   20.11527  14.812  < 2e-16 ***
## brandhtc               468.33621   83.42966   5.614 1.99e-08 ***
## brandhuawei            181.21265   19.65510   9.220  < 2e-16 ***
## brandhuion              83.38371   69.03443   1.208 0.227105    
## brandhuntkey            13.70394   31.22200   0.439 0.660721    
## brandhurom             298.19371  116.38201   2.562 0.010402 *  
## brandhuter             168.18871   35.41392   4.749 2.04e-06 ***
## brandhygge             631.53371  163.44203   3.864 0.000112 ***
## brandhyperx             70.04210   21.56202   3.248 0.001161 ** 
## brandhyundai           131.52871  116.38201   1.130 0.258417    
## brandid-cooling          6.49943   47.51275   0.137 0.891194    
## brandideal               1.20371   32.16629   0.037 0.970149    
## brandikins              -0.41629  163.44203  -0.003 0.997968    
## brandimetec             24.87496   44.97010   0.553 0.580165    
## brandincase             94.59010   23.64614   4.000 6.33e-05 ***
## brandindesit           292.47236   20.89949  13.994  < 2e-16 ***
## brandinhouse            12.91660   22.91376   0.564 0.572956    
## brandinkax               1.20371  163.44203   0.007 0.994124    
## brandinoi               22.73371  163.44203   0.139 0.889377    
## brandinsight            11.55371   95.68313   0.121 0.903889    
## brandinspector         184.19371   83.42966   2.208 0.027262 *  
## brandintel             203.43167   31.22200   6.516 7.27e-11 ***
## brandintex             174.87538   50.70501   3.449 0.000563 ***
## brandionkini            19.44371  163.44203   0.119 0.905304    
## brandipower              5.22578   21.88887   0.239 0.811306    
## brandiqos               34.06955   38.38777   0.888 0.374806    
## brandirbis             221.34571   46.17410   4.794 1.64e-06 ***
## brandivi                 6.26654   25.73939   0.243 0.807649    
## brandivolia             66.71371  163.44203   0.408 0.683143    
## brandiwalk               0.74371   75.12426   0.010 0.992101    
## brandjabra              29.53371   40.37808   0.731 0.464518    
## brandjaguar            126.52249   30.22804   4.186 2.85e-05 ***
## brandjandeks           120.81976   31.44413   3.842 0.000122 ***
## brandjanome            186.84454   21.61160   8.646  < 2e-16 ***
## brandjbl                46.54844   20.68538   2.250 0.024431 *  
## brandjetair             63.82515   24.22685   2.634 0.008428 ** 
## brandjetpik             75.97371  163.44203   0.465 0.642050    
## brandjoby               41.71594   57.46811   0.726 0.467903    
## brandjoerex             19.64371   95.68313   0.205 0.837338    
## brandjonsbo             19.37371  116.38201   0.166 0.867790    
## brandjvc                50.50871  116.38201   0.434 0.664296    
## brandkaabo             519.64605   35.41392  14.673  < 2e-16 ***
## brandkama               27.59371   83.42966   0.331 0.740840    
## brandkarcher           165.58669   30.60403   5.411 6.29e-08 ***
## brandkaspersky          13.97592   26.12448   0.535 0.592669    
## brandkenko               8.84705   95.68313   0.092 0.926331    
## brandkenwood           221.15301   22.04499  10.032  < 2e-16 ***
## brandkicx               97.50205   69.03443   1.412 0.157844    
## brandking              147.73371   57.46811   2.571 0.010150 *  
## brandkingston           47.09641   25.29060   1.862 0.062576 .  
## brandkitchenaid        719.05190   52.63574  13.661  < 2e-16 ***
## brandkivi              219.90371   43.88032   5.011 5.41e-07 ***
## brandkmk                 1.90371  116.38201   0.016 0.986949    
## brandkomax               1.87238   21.44419   0.087 0.930422    
## brandkosadaka           -1.33629  163.44203  -0.008 0.993477    
## brandkramet              6.23934   44.97010   0.139 0.889653    
## brandkrups             629.04943   47.51275  13.240  < 2e-16 ***
## brandkumano              4.47371  163.44203   0.027 0.978163    
## brandkumho              56.53371  163.44203   0.346 0.729423    
## brandkurzweil         1106.29371  163.44203   6.769 1.31e-11 ***
## brandkyocera           113.01371   95.68313   1.181 0.237556    
## brandlamart             -0.41829   75.12426  -0.006 0.995557    
## brandlaurastar        1244.95371  116.38201  10.697  < 2e-16 ***
## brandlavazza             8.42959   23.37007   0.361 0.718324    
## brandlego               28.52460   23.59310   1.209 0.226656    
## brandlegrand            22.90921   41.14725   0.557 0.577691    
## brandlenovo            532.19713   20.15540  26.405  < 2e-16 ***
## brandlenspen            11.16371  116.38201   0.096 0.923582    
## brandlg                468.39106   19.65838  23.827  < 2e-16 ***
## brandlihom             148.71260   57.46811   2.588 0.009662 ** 
## brandlion               -0.69629  163.44203  -0.004 0.996601    
## brandloewe            4626.90371  163.44203  28.309  < 2e-16 ***
## brandlogitech           27.50277   20.33329   1.353 0.176187    
## brandlol                 4.21371  163.44203   0.026 0.979432    
## brandlori               -0.86629  116.38201  -0.007 0.994061    
## brandlotte             697.50371  116.38201   5.993 2.06e-09 ***
## brandlowepro            25.04371   95.68313   0.262 0.793525    
## brandluch               -1.73629  163.44203  -0.011 0.991524    
## brandlumax              15.56157   47.51275   0.328 0.743272    
## brandluminarc           75.12958   35.83878   2.096 0.036056 *  
## brandluxell             28.13705   95.68313   0.294 0.768709    
## brandmaestro            15.12581   21.41371   0.706 0.479965    
## brandmakita            353.63371   83.42966   4.239 2.25e-05 ***
## brandmanfrotto          60.31826   52.63574   1.146 0.251816    
## brandmarcato            83.12154   39.00427   2.131 0.033084 *  
## brandmarcel              0.51371  163.44203   0.003 0.997492    
## brandmarley             66.71871  116.38201   0.573 0.566461    
## brandmarshall          143.87871   69.03443   2.084 0.037148 *  
## brandmart              182.40295   37.27207   4.894 9.90e-07 ***
## brandmarvel             55.14371  163.44203   0.337 0.735823    
## brandmatrix              8.53705   95.68313   0.089 0.928906    
## brandmattel              1.71998   23.12792   0.074 0.940718    
## brandmaxwell            16.72067   20.86057   0.802 0.422818    
## brandmcdavid             9.88371  116.38201   0.085 0.932321    
## brandmedisana           50.50871  116.38201   0.434 0.664296    
## brandmegogo              6.26080   22.95084   0.273 0.785014    
## brandmercusys           15.80859   32.42765   0.488 0.625903    
## brandmetabo             44.57038   95.68313   0.466 0.641351    
## brandmetalions          16.71371  116.38201   0.144 0.885808    
## brandmichelin          123.42371  163.44203   0.755 0.450159    
## brandmicro             228.75371  163.44203   1.400 0.161635    
## brandmicrolab           29.19607   22.89552   1.275 0.202245    
## brandmicrosoft         109.28416   22.87746   4.777 1.78e-06 ***
## brandmidea             174.62724   21.10810   8.273  < 2e-16 ***
## brandmilight            10.62038   95.68313   0.111 0.911620    
## brandmirage             43.56371  163.44203   0.267 0.789824    
## brandmisty             221.67371   44.97010   4.929 8.26e-07 ***
## brandmlife               4.21371   50.70501   0.083 0.933770    
## brandmonge              10.58371  163.44203   0.065 0.948369    
## brandmonkart            26.43371  163.44203   0.162 0.871518    
## brandmoshi              28.10371   37.81172   0.743 0.457329    
## brandmotorola           47.98371  163.44203   0.294 0.769077    
## brandmoulinex          101.66436   20.14045   5.048 4.48e-07 ***
## brandmoxom               8.84371   69.03443   0.128 0.898065    
## brandmsi               391.56553   52.63574   7.439 1.02e-13 ***
## brandmueller             0.51371  163.44203   0.003 0.997492    
## brandmujjo               0.92371   41.98100   0.022 0.982445    
## brandmuljhtidom          0.84402   20.82964   0.041 0.967678    
## brandnavien            637.89371   60.56712  10.532  < 2e-16 ***
## brandnavitel            77.13371  163.44203   0.472 0.636975    
## brandneo                34.54794   19.73741   1.750 0.080056 .  
## brandneoline           138.49275   28.30256   4.893 9.93e-07 ***
## brandneptun             31.51705   95.68313   0.329 0.741862    
## brandnika               20.83709   21.63355   0.963 0.335457    
## brandnikon             773.50467   40.37808  19.157  < 2e-16 ***
## brandninebot           460.32955   38.38777  11.992  < 2e-16 ***
## brandnintendo          181.23097   29.87736   6.066 1.32e-09 ***
## brandnivea               0.14371   33.92437   0.004 0.996620    
## brandnokia              39.96841   22.35826   1.788 0.073837 .  
## brandnokian             42.87371  163.44203   0.262 0.793077    
## brandnommi             140.79371  163.44203   0.861 0.389004    
## brandnone               44.74187   20.49196   2.183 0.029009 *  
## brandnordland           16.72934   44.97010   0.372 0.709886    
## brandnovatrack         167.40971   75.12426   2.228 0.025853 *  
## brandnuk                10.60371  163.44203   0.065 0.948272    
## brandnv-print           12.35705   50.70501   0.244 0.807460    
## brandnzxt              187.60621   83.42966   2.249 0.024535 *  
## brandockel             124.58371  163.44203   0.762 0.445912    
## brandokko               13.07775   23.46617   0.557 0.577322    
## brandokuma              42.79371   95.68313   0.447 0.654700    
## brandolimpik            -1.12586   30.60403  -0.037 0.970654    
## brandolympus            82.92371  163.44203   0.507 0.611904    
## brandomron              46.77284   30.80241   1.518 0.128896    
## brandoppo              195.91449   19.77705   9.906  < 2e-16 ***
## brandoptoma            552.82371  163.44203   3.382 0.000719 ***
## brandoral-b             27.21466   26.19335   1.039 0.298811    
## brandorgan              -1.25709   23.49093  -0.054 0.957323    
## brandorico              13.77514   64.33257   0.214 0.830451    
## brandosz                21.87401   27.73687   0.789 0.430332    
## brandowner              -1.33629  163.44203  -0.008 0.993477    
## brandozone               7.05734   27.53071   0.256 0.797686    
## brandpaclan              8.67121   83.42966   0.104 0.917222    
## brandpalisad             4.79705   69.03443   0.069 0.944601    
## brandpalit             250.20371   69.03443   3.624 0.000290 ***
## brandpanasonic          66.90055   20.27970   3.299 0.000971 ***
## brandpaperline           8.84371  163.44203   0.054 0.956848    
## brandpasabahce           0.96145   20.69276   0.046 0.962941    
## brandpastel             44.17353   24.76922   1.783 0.074523 .  
## brandpatriot            48.20201   31.91568   1.510 0.130972    
## brandpccooler            9.19371  116.38201   0.079 0.937036    
## brandpemco               6.17871  116.38201   0.053 0.957660    
## brandperilla            33.12550   21.68651   1.527 0.126647    
## brandpeterhof            6.81577   22.06589   0.309 0.757411    
## brandpetzl              37.54871  116.38201   0.323 0.746974    
## brandpgytech             8.07371   95.68313   0.084 0.932755    
## brandphantom            96.80371  163.44203   0.592 0.553663    
## brandphilips            78.56929   19.68125   3.992 6.55e-05 ***
## brandpixel             136.16371  116.38201   1.170 0.242015    
## brandplantronics        32.24615   31.91568   1.010 0.312328    
## brandplayme            275.04371  163.44203   1.683 0.092412 .  
## brandplextor            55.83371  163.44203   0.342 0.732644    
## brandpocketbook        177.68371   32.42765   5.479 4.28e-08 ***
## brandpolaris            36.28730   19.76590   1.836 0.066382 .  
## brandpolaroid            0.04871   83.42966   0.001 0.999534    
## brandpolimerbiht         0.44796   20.10849   0.022 0.982227    
## brandportcase            0.69371   42.88838   0.016 0.987095    
## brandpowerplant         30.46571   75.12426   0.406 0.685083    
## brandpowertrac          33.78621   60.56712   0.558 0.576961    
## brandpozis             336.42161   26.88464  12.514  < 2e-16 ***
## brandpresident         334.07371  163.44203   2.044 0.040957 *  
## brandprestigio          61.18613   35.83878   1.707 0.087776 .  
## brandprocab              6.53371  163.44203   0.040 0.968113    
## brandpromtorgservis     25.04371  163.44203   0.153 0.878220    
## brandproscreen         177.36371  163.44203   1.085 0.277845    
## brandprovence            1.85712   21.23829   0.087 0.930320    
## brandpyrex              14.24826   24.37017   0.585 0.558778    
## brandrapoo              36.15324   31.67517   1.141 0.253716    
## brandrastar             27.17191   27.24034   0.997 0.318530    
## brandrazer             130.90557   31.44413   4.163 3.14e-05 ***
## brandredmond            44.12845   20.32816   2.171 0.029948 *  
## brandregnum             74.08281   34.26859   2.162 0.030633 *  
## brandremington          39.13142   22.59682   1.732 0.083326 .  
## brandresanta            52.52800   47.51275   1.106 0.268921    
## brandresto              14.82705   69.03443   0.215 0.829941    
## brandrioba               0.97371  163.44203   0.006 0.995247    
## brandritmix              6.20086   40.37808   0.154 0.877949    
## brandriva               25.04871  116.38201   0.215 0.829590    
## brandrivacase           26.67320   28.81546   0.926 0.354627    
## brandroadx              41.64038   95.68313   0.435 0.663425    
## brandrockstar           57.45371   35.83878   1.603 0.108912    
## brandrondell            23.17180   20.15287   1.150 0.250228    
## brandrosneftjh           1.67371  163.44203   0.010 0.991829    
## brandrossija            14.17038   95.68313   0.148 0.882267    
## brandrowenta            39.77443   20.17631   1.971 0.048687 *  
## brandruggear            52.59371   69.03443   0.762 0.446153    
## brandsakura             -1.57629  163.44203  -0.010 0.992305    
## brandsamsonite         112.35229   64.33257   1.746 0.080739 .  
## brandsamsung           247.30580   19.43897  12.722  < 2e-16 ***
## brandsamura             24.58371  163.44203   0.150 0.880439    
## brandsanc              207.74408   36.76534   5.651 1.60e-08 ***
## brandsaramonic          67.37657   64.33257   1.047 0.294956    
## brandsatechi            80.48746   60.56712   1.329 0.183884    
## brandsavic              14.80871   83.42966   0.177 0.859116    
## brandsbs                 3.44407   29.09550   0.118 0.905774    
## brandscarlett           20.01984   19.97912   1.002 0.316327    
## brandschwiizer          18.10371  163.44203   0.111 0.911803    
## brandscreentec          -2.47629   60.56712  -0.041 0.967388    
## brandseagate            87.55038   95.68313   0.915 0.360192    
## brandseasonic          258.84371  163.44203   1.584 0.113264    
## brandselect             -1.57629  163.44203  -0.010 0.992305    
## brandsencor             50.53554   23.41754   2.158 0.030928 *  
## brandsennheiser        210.23371  163.44203   1.286 0.198345    
## brandshelkovica         11.18371  163.44203   0.068 0.945446    
## brandship                6.28945   22.15294   0.284 0.776479    
## brandsibrtekh           -1.10629  163.44203  -0.007 0.994599    
## brandsigma             344.49371  163.44203   2.108 0.035055 *  
## brandsimax               9.29259   22.46591   0.414 0.679145    
## brandsimfer            121.83038   31.67517   3.846 0.000120 ***
## brandsinger            160.80136   43.88032   3.665 0.000248 ***
## brandsjcam             113.78205   69.03443   1.648 0.099316 .  
## brandskullcandy          8.84371  163.44203   0.054 0.956848    
## brandsmart               9.54371  163.44203   0.058 0.953436    
## brandsmeg              326.74705   95.68313   3.415 0.000638 ***
## brandsmile             501.25371  163.44203   3.067 0.002164 ** 
## brandsony              211.10402   19.94483  10.584  < 2e-16 ***
## brandsparta              0.51371  163.44203   0.003 0.997492    
## brandspiegelau          20.47721   41.14725   0.498 0.618727    
## brandspigen             -2.14471   41.98100  -0.051 0.959256    
## brandsportop           460.23371  163.44203   2.816 0.004865 ** 
## brandsports            719.49571   75.12426   9.577  < 2e-16 ***
## brandstaedtler          -1.33629  163.44203  -0.008 0.993477    
## brandstarline          127.64962   39.66589   3.218 0.001291 ** 
## brandstatus             12.54571   75.12426   0.167 0.867371    
## brandstaub             170.65171   75.12426   2.272 0.023113 *  
## brandsteelseries        92.32657   36.28847   2.544 0.010953 *  
## brandstels             249.35371  163.44203   1.526 0.127102    
## brandsumdex             22.36429   29.71070   0.753 0.451610    
## brandsuperlux           92.17371   69.03443   1.335 0.181819    
## brandsvc                26.83614   22.39773   1.198 0.230856    
## brandsvetocopy           1.46371   31.00825   0.047 0.962351    
## brandsynology          606.09371  163.44203   3.708 0.000209 ***
## brandtacx              830.60371  163.44203   5.082 3.74e-07 ***
## brandtailg             493.61657   47.51275  10.389  < 2e-16 ***
## brandtamron            830.60371   75.12426  11.056  < 2e-16 ***
## brandtaoran            251.90371  163.44203   1.541 0.123261    
## brandtayfun              2.63271   32.16629   0.082 0.934769    
## brandtcl               249.45962   22.02441  11.327  < 2e-16 ***
## brandtechnodom           9.88419   20.09103   0.492 0.622741    
## brandtechnogym        4491.71371  163.44203  27.482  < 2e-16 ***
## brandtechnomax         109.30371  163.44203   0.669 0.503649    
## brandtefal              77.00286   19.58151   3.932 8.41e-05 ***
## brandtemdan             -2.46429   75.12426  -0.033 0.973832    
## brandtenda               6.53371  163.44203   0.040 0.968113    
## brandthefaceshop         3.98371   21.77501   0.183 0.854838    
## brandthermaltake        61.48746   38.38777   1.602 0.109214    
## brandthermex           104.54697   22.49406   4.648 3.36e-06 ***
## brandthomas            198.44025   26.97044   7.358 1.88e-13 ***
## brandthule              87.54371  163.44203   0.536 0.592218    
## brandtigar              87.54371  163.44203   0.536 0.592218    
## brandtigernu            43.56371  163.44203   0.267 0.789824    
## brandtimberk            60.92871  116.38201   0.524 0.600611    
## brandtimson              6.74903   34.63057   0.195 0.845482    
## brandtion              582.92371  163.44203   3.567 0.000362 ***
## brandtoday              -0.41629  163.44203  -0.003 0.997968    
## brandtopperr            11.80524   30.80241   0.383 0.701530    
## brandtornado            31.98871   83.42966   0.383 0.701408    
## brandtoro                0.99652   21.25342   0.047 0.962603    
## brandtoshiba            40.12050   36.28847   1.106 0.268902    
## brandtoyo               78.28871  116.38201   0.673 0.501147    
## brandtp-link            28.94911   20.39236   1.420 0.155725    
## brandtramp              17.20943   64.33257   0.268 0.789079    
## brandtranscend          25.56209   20.21679   1.264 0.206089    
## brandtribe             316.71371   75.12426   4.216 2.49e-05 ***
## brandtrio                0.47104   27.33474   0.017 0.986251    
## brandtrust              27.93742   23.39366   1.194 0.232390    
## brandtucano             32.20771   37.81172   0.852 0.394331    
## brandturbo              -1.57295   95.68313  -0.016 0.986884    
## brandtvs                27.35345   20.13479   1.359 0.174302    
## brandtyr                23.89371  163.44203   0.146 0.883771    
## brandubisoft            44.72371  116.38201   0.384 0.700769    
## brandUnknown             9.01750   19.42622   0.464 0.642511    
## brandurbanears         159.30371  163.44203   0.975 0.329721    
## branduriage             11.02371  163.44203   0.067 0.946226    
## brandusams               5.21038   35.41392   0.147 0.883031    
## branduteki               2.60676   30.80241   0.085 0.932557    
## brandvarta               1.85437   21.25342   0.087 0.930472    
## brandventa             280.83871  116.38201   2.413 0.015820 *  
## brandviatti             49.54538   69.03443   0.718 0.472949    
## brandvictoria           22.70874   22.87746   0.993 0.320895    
## brandvikhrjh            57.93205   33.28406   1.741 0.081768 .  
## brandvirtuix            12.31371  163.44203   0.075 0.939944    
## brandvitehks            -0.46829   54.86300  -0.009 0.993190    
## brandvitek              24.62175   19.84326   1.241 0.214678    
## brandvivo              163.45964   23.32371   7.008 2.43e-12 ***
## brandvoin               20.42371  163.44203   0.125 0.900555    
## brandvortex              2.95371  116.38201   0.025 0.979752    
## brandwacom             161.95443   47.51275   3.409 0.000653 ***
## brandweber              14.45871   83.42966   0.173 0.862413    
## brandwethepeople       483.38371  163.44203   2.958 0.003102 ** 
## brandwhirlpool        1056.29871   83.42966  12.661  < 2e-16 ***
## brandwilmax              7.71071   25.29060   0.305 0.760455    
## brandwilson             10.92371  163.44203   0.067 0.946713    
## brandwintek             29.38871   60.56712   0.485 0.627517    
## brandwmf               307.22371   75.12426   4.090 4.33e-05 ***
## brandwonlex             36.62371  163.44203   0.224 0.822697    
## brandwxd                 8.84371  116.38201   0.076 0.939428    
## brandx-game             19.21059   21.22340   0.905 0.365382    
## brandxbox              310.56201   31.91568   9.731  < 2e-16 ***
## brandxerox             155.14121   83.42966   1.860 0.062952 .  
## brandxiaomi            131.58192   19.84741   6.630 3.38e-11 ***
## brandxp-pen            165.53910   49.01195   3.378 0.000732 ***
## brandyokohama           82.92038   95.68313   0.867 0.386155    
## brandyonker             64.40371  163.44203   0.394 0.693548    
## brandyoobao             24.23141   32.42765   0.747 0.454917    
## brandzala               -0.64629   83.42966  -0.008 0.993819    
## brandzalman             96.34371  116.38201   0.828 0.407772    
## brandzeppelin           23.66371  163.44203   0.145 0.884882    
## brandzhiyun            206.56788   50.70501   4.074 4.63e-05 ***
## brandzhorka             -1.18629  116.38201  -0.010 0.991867    
## brandzowie              82.48371   44.97010   1.834 0.066628 .  
## brandzugo               25.07371   75.12426   0.334 0.738559    
## brandzwilling           83.68018   43.88032   1.907 0.056522 .  
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 162.3 on 117704 degrees of freedom
## Multiple R-squared:  0.4836, Adjusted R-squared:  0.4812 
## F-statistic: 194.4 on 567 and 117704 DF,  p-value: < 2.2e-16

Interpretation

A Simple Linear Regression model was developed using brand as the predictor variable and price as the response variable. This model serves as a baseline to examine the influence of brand on product price before incorporating additional predictors in the Multiple Linear Regression model.

5.5 Multiple Linear Regression

multiple_model <- lm(
  price ~ brand + category_code,
  data = train_data
)

summary(multiple_model)
## 
## Call:
## lm(formula = price ~ brand + category_code, data = train_data)
## 
## Residuals:
##    Min     1Q Median     3Q    Max 
## -818.8  -33.3   -0.1    7.7 5033.4 
## 
## Coefficients: (3 not defined because of singularities)
##                                                       Estimate Std. Error
## (Intercept)                                         -3.884e+01  2.070e+01
## brandaccesstyle                                      2.803e+01  5.638e+01
## brandaction                                          2.273e+01  1.432e+02
## brandadidas                                          3.940e+01  1.020e+02
## brandadvantek                                        1.167e+01  2.718e+01
## brandaeg                                             5.376e+02  6.064e+01
## brandaerocool                                        3.817e+01  3.378e+01
## brandaimoto                                          4.327e+01  2.891e+01
## brandairline                                         8.480e+00  2.753e+01
## brandakku                                            6.591e+01  7.312e+01
## brandaksion                                          2.728e+01  1.972e+01
## brandakvafor                                         6.634e+00  1.752e+01
## brandalex                                            6.764e+01  1.432e+02
## brandalfa                                            1.423e+01  1.850e+02
## brandalienware                                       3.618e+03  1.432e+02
## brandalmatv                                          2.042e+01  1.020e+02
## brandaltair                                          3.430e+01  1.432e+02
## brandaltel                                           1.327e+02  2.954e+01
## brandaltex                                           1.941e+02  4.172e+01
## brandamazon                                          1.013e+02  8.428e+01
## brandamd                                             8.717e+01  3.155e+01
## brandamigami                                        -4.163e-01  3.759e+01
## brandanymode                                         3.502e+01  2.628e+01
## brandaoc                                            -1.570e+02  2.256e+01
## brandaoki                                            7.626e+01  4.836e+01
## brandapc                                            -2.267e+02  4.825e+01
## brandapollo                                          6.965e+00  2.144e+01
## brandapple                                           5.332e+02  1.730e+01
## brandaqua                                           -1.367e+02  4.549e+01
## brandaquadent                                        5.347e+01  5.037e+01
## brandaquael                                          3.546e+01  1.432e+02
## brandaquapick                                        7.829e+01  4.295e+01
## brandarena                                           1.787e+01  1.432e+02
## brandariston                                        -4.356e+01  2.385e+01
## brandarktika                                         4.491e+01  5.312e+01
## brandarnica                                          3.807e+01  8.392e+01
## brandart.fit                                         2.137e+01  4.784e+01
## brandartberry                                       -5.063e-01  1.432e+02
## brandartel                                           1.302e+02  4.613e+01
## brandasrock                                          1.251e+02  4.819e+01
## brandastonish                                        1.386e+01  8.386e+01
## brandasus                                            2.006e+02  1.842e+01
## brandatlant                                         -5.883e+01  2.132e+01
## brandatmor                                          -1.287e+02  4.689e+01
## brandatom                                            2.042e+01  1.432e+02
## brandaudac                                          -4.249e+01  1.440e+02
## brandaura                                           -2.546e+00  1.020e+02
## brandausini                                          6.705e+00  2.092e+01
## brandauthor                                          1.920e+02  1.521e+02
## brandava                                             6.388e+00  1.717e+01
## brandavermedia                                       1.576e+02  8.888e+01
## brandavrora                                         -1.035e+00  2.480e+01
## brandawax                                           -1.364e+02  1.862e+01
## brandawei                                            8.157e+01  2.764e+01
## brandbaboo                                           2.042e+01  1.432e+02
## brandbabyliss                                        5.216e+01  2.265e+01
## brandbaltextile                                      9.900e+01  1.020e+02
## brandbarbie                                         -1.858e+01  9.293e+01
## brandbardahl                                         2.134e+01  1.432e+02
## brandbarjher                                         3.794e+00  1.833e+01
## brandbarkan                                          3.441e+01  1.915e+01
## brandbeats                                           2.767e+02  5.645e+01
## brandbeeline                                         1.266e+02  3.121e+01
## brandbeko                                            3.706e+01  1.763e+01
## brandbelcando                                       -2.764e+01  1.460e+02
## brandbelita                                         -1.241e+01  8.426e+01
## brandbelitam                                         3.737e-01  1.432e+02
## brandbellissima                                      4.259e+01  2.501e+01
## brandbequiet                                         2.819e+02  7.391e+01
## brandberghoff                                        2.195e+01  1.835e+01
## brandberkley                                         2.594e+00  1.432e+02
## brandberry                                           3.430e+01  1.432e+02
## brandbestway                                         2.132e+01  5.037e+01
## brandbeurer                                          4.137e+01  2.200e+01
## brandbfgoodrich                                      5.352e+01  1.432e+02
## brandbioderma                                        2.160e+01  1.432e+02
## brandbiol                                            4.555e+00  3.426e+01
## brandbiolane                                         4.822e+01  1.433e+02
## brandbiostar                                         1.015e+02  8.784e+01
## brandbirjusa                                        -1.184e+02  1.947e+01
## brandbisfree                                         9.737e-01  1.432e+02
## brandblackstar                                       1.786e+02  1.021e+02
## brandblehk                                           4.211e+01  1.433e+02
## brandbloody                                          7.969e+01  1.918e+01
## brandbona                                            7.736e+01  3.104e+01
## brandborasco                                        -1.923e+00  3.606e+01
## brandbork                                            3.016e+02  2.128e+01
## brandborner                                          7.293e+01  6.591e+01
## brandbosch                                           2.043e+02  1.751e+01
## brandbose                                            3.723e+02  5.312e+01
## brandbradex                                          9.930e+00  3.319e+01
## brandbrateck                                         1.362e+02  1.432e+02
## brandbraun                                           8.778e+01  1.774e+01
## brandbrelil                                          8.154e+00  1.432e+02
## brandbridgestone                                     9.457e+01  8.386e+01
## brandbrother                                         5.297e+02  6.136e+01
## brandbruder                                          5.329e+01  1.432e+02
## brandbuebchen                                        1.924e+00  1.432e+02
## brandbuff                                            2.088e+01  1.432e+02
## brandbushido                                         8.147e+00  3.141e+01
## brandbyintek                                         2.708e+02  1.604e+02
## brandbykski                                          2.626e+01  5.038e+01
## brandcablexpert                                      6.472e+00  1.062e+02
## brandcalgon                                          4.914e+00  1.432e+02
## brandcamelion                                       -8.709e+01  2.193e+01
## brandcannondale                                      1.011e+03  1.521e+02
## brandcanon                                           3.263e+02  2.094e+01
## brandcanyon                                         -1.965e+02  6.071e+01
## brandcasada                                          5.804e+02  1.436e+02
## brandcasio                                          -7.286e+01  1.245e+02
## brandcaso                                            1.570e+02  4.627e+01
## brandcaspio                                          8.986e+01  5.638e+01
## brandcatrice                                        -6.363e-01  1.432e+02
## brandcdc                                             7.387e+00  4.808e+01
## brandcelebrat                                        9.551e+01  1.433e+02
## brandchicco                                          1.616e+01  3.664e+01
## brandchina                                          -3.499e+02  2.119e+01
## brandcilek                                           5.469e+02  2.075e+01
## brandcliny                                          -2.546e+02  1.438e+02
## brandcollecta                                        5.137e-01  1.020e+02
## brandcolorful                                        4.308e+01  4.676e+01
## brandcompliment                                     -8.384e+00  2.634e+01
## brandcontinent                                      -7.086e+01  2.322e+01
## brandcontinental                                     1.480e+02  1.020e+02
## brandcoolinar                                        1.664e+01  2.115e+01
## brandcort                                            2.274e+02  1.432e+02
## brandcougar                                          5.789e+01  4.384e+01
## brandcremesso                                        8.429e+00  2.604e+01
## brandcullmann                                       -1.235e+02  4.186e+01
## brandcyberpower                                     -3.521e+02  1.434e+02
## brandd-color                                         1.347e+01  1.432e+02
## brandd-link                                          1.017e+02  4.047e+01
## branddaewoo                                          8.882e+01  6.056e+01
## branddaikin                                          3.655e+02  1.433e+02
## branddaiwa                                           3.870e+01  1.432e+02
## branddam                                            -2.036e+00  1.432e+02
## branddarina                                          1.881e+02  8.386e+01
## branddc-girls                                       -3.015e+01  5.982e+01
## branddecoroom                                        6.849e+01  1.700e+02
## branddeepcool                                       -1.341e+02  2.381e+01
## branddeerma                                          3.662e+01  1.020e+02
## branddefender                                        1.679e+01  6.226e+01
## branddell                                            2.570e+02  4.082e+01
## branddelonghi                                        2.257e+02  1.884e+01
## branddelux                                           6.211e+01  1.900e+01
## branddeluxe                                          3.587e+01  1.793e+01
## branddemidovskiy                                     6.139e+00  4.355e+01
## branddepileve                                        1.864e+00  1.432e+02
## branddermal                                         -1.776e+00  8.386e+01
## branddermoviva                                       6.537e-01  2.917e+01
## branddesignskin                                     -8.283e-01  6.584e+01
## branddifferent                                      -1.247e+02  2.026e+01
## branddji                                             4.272e+02  2.309e+01
## branddogland                                         7.190e+01  2.441e+01
## branddomini                                          1.008e+02  8.453e+01
## branddougez                                          7.772e+00  1.462e+02
## branddr.beckmann                                    -4.163e-01  5.037e+01
## brandduracell                                       -8.093e+01  2.655e+01
## branddxracer                                         1.841e+02  4.003e+01
## branddyson                                           5.432e+02  2.391e+01
## brande.gov                                           1.116e+01  2.776e+01
## brandecocool                                         5.977e+01  3.068e+01
## brandecologystone                                    7.111e+01  7.661e+01
## brandedifier                                         1.102e+02  3.774e+01
## brandeglo                                            3.386e+01  1.020e+02
## brandegoiste                                        -4.163e-01  7.312e+01
## brandehlektrostandart                                2.273e+01  1.432e+02
## brandehra                                           -1.057e+02  2.850e+01
## brandelari                                           3.291e+01  2.540e+01
## brandelectrolux                                      2.837e+02  1.812e+01
## brandemsa                                            3.263e+01  3.606e+01
## brandenergea                                        -7.844e+00  3.550e+01
## brandepson                                           2.994e+02  2.087e+01
## brandergolux                                        -1.207e+02  2.259e+01
## brandeset                                           -2.091e+02  2.004e+01
## brandetalon                                         -6.557e+01  1.440e+02
## brandeuroprint                                       3.054e+02  6.686e+01
## brandeverlast                                        5.745e+01  1.432e+02
## brandeyfel                                          -1.360e+02  1.528e+02
## brandezviz                                           5.074e+01  7.312e+01
## brandfender                                          4.137e+02  1.432e+02
## brandfiltero                                        -2.883e+00  2.310e+01
## brandfissman                                         1.693e+01  1.926e+01
## brandfitokosmetik                                   -1.686e+00  1.432e+02
## brandfixsen                                          1.292e+01  1.432e+02
## brandfizan                                           1.324e+01  1.432e+02
## brandflama                                           1.311e+02  3.141e+01
## brandfly                                            -1.095e+02  8.389e+01
## brandforward                                         1.940e+02  1.432e+02
## brandfossil                                          1.179e+02  4.613e+01
## brandfranke                                          1.359e+02  1.037e+02
## brandfujifilm                                        2.458e+02  2.495e+01
## brandgalaxy                                          2.688e+01  8.396e+01
## brandgamdias                                         7.407e+01  6.303e+01
## brandgamemax                                         3.761e+01  2.450e+01
## brandgarmin                                          7.162e+02  2.863e+01
## brandgefest                                          2.767e+02  2.576e+01
## brandgembird                                         3.347e+01  1.467e+02
## brandgenau                                           2.705e+02  1.054e+02
## brandgeneris                                         1.014e+02  1.432e+02
## brandgenius                                          3.030e+01  1.864e+01
## brandgerat                                           5.961e+00  2.576e+01
## brandgewa                                            4.409e+01  7.312e+01
## brandgeyzer                                          1.874e+00  5.308e+01
## brandgezatone                                        4.656e+01  2.527e+01
## brandggg                                             1.313e+01  2.130e+01
## brandgiant                                           5.207e+02  1.141e+02
## brandgigabyte                                        1.962e+02  3.096e+01
## brandgillette                                        5.664e+00  7.312e+01
## brandgiottos                                        -2.949e+02  1.433e+02
## brandglasslock                                       7.164e+00  2.431e+01
## brandglassware                                       1.609e+01  2.404e+01
## brandglobal                                          1.010e+02  3.022e+01
## brandgo-sport                                        7.785e+02  1.432e+02
## brandgolf                                           -1.546e+00  1.432e+02
## brandgoodride                                        4.611e+01  1.865e+01
## brandgoodyear                                       -5.711e+01  6.525e+01
## brandgopro                                           1.603e+02  3.003e+01
## brandgorenje                                         5.997e+01  1.871e+01
## brandgrans                                           3.865e+01  2.540e+01
## brandgreenway                                        1.875e+02  5.396e+01
## brandgrillver                                        6.208e+01  1.432e+02
## brandgrohe                                           1.603e+02  1.770e+01
## brandgtec                                            6.546e+00  4.444e+01
## brandgutrend                                         2.620e+02  3.772e+01
## brandhabilead                                        4.565e+01  2.090e+01
## brandhansa                                           1.966e+02  1.832e+01
## brandhaushalt                                        1.059e+01  3.188e+01
## brandhenkel                                          4.640e+00  6.050e+01
## brandherschel                                        8.670e+01  1.021e+02
## brandhintek                                          4.996e+01  1.129e+02
## brandhitachi                                         1.787e+03  1.021e+02
## brandhms                                             1.372e+02  1.528e+02
## brandhoco                                           -1.474e+00  3.314e+01
## brandhonor                                          -9.319e+00  1.812e+01
## brandhotpoint-ariston                                9.134e+01  1.890e+01
## brandhp                                              2.745e+02  1.865e+01
## brandhtc                                             4.683e+02  7.312e+01
## brandhuawei                                          7.226e+01  1.736e+01
## brandhuion                                          -7.475e+00  6.075e+01
## brandhuntkey                                        -3.001e+02  2.800e+01
## brandhurom                                           2.569e+02  1.025e+02
## brandhuter                                           1.330e+02  4.179e+01
## brandhygge                                           6.315e+02  1.432e+02
## brandhyperx                                          1.217e+02  1.926e+01
## brandhyundai                                        -3.780e+01  1.031e+02
## brandid-cooling                                      1.539e+02  4.412e+01
## brandideal                                           1.204e+00  2.819e+01
## brandikins                                          -4.163e-01  1.432e+02
## brandimetec                                          3.772e+01  3.957e+01
## brandincase                                          9.459e+01  2.072e+01
## brandindesit                                        -3.329e+01  1.855e+01
## brandinhouse                                         1.588e+01  2.011e+01
## brandinkax                                           9.698e+01  1.434e+02
## brandinoi                                            7.022e+01  1.436e+02
## brandinsight                                        -5.860e+01  8.387e+01
## brandinspector                                       2.063e+02  7.499e+01
## brandintel                                           8.642e+01  2.895e+01
## brandintex                                           1.749e+02  4.444e+01
## brandionkini                                         1.944e+01  1.432e+02
## brandipower                                         -3.500e+02  2.000e+01
## brandiqos                                            3.407e+01  3.364e+01
## brandirbis                                          -1.339e+02  4.086e+01
## brandivi                                            -3.553e+02  2.283e+01
## brandivolia                                          7.025e+01  1.434e+02
## brandiwalk                                           7.437e-01  6.584e+01
## brandjabra                                           5.286e+01  3.540e+01
## brandjaguar                                          9.682e+01  3.065e+01
## brandjandeks                                         1.316e+02  2.842e+01
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## category_code19.49                                  -2.123e-10  5.161e+01
## category_code19.68                                  -2.330e-10  3.463e+01
## category_code19.95                                  -2.128e-10  2.242e+01
## category_code2.29                                   -2.881e-10  3.127e+01
## category_code2.31                                   -1.666e-10  3.127e+01
## category_code2.52                                   -2.075e-10  4.881e+01
## category_code2.78                                   -2.029e-10  3.463e+01
## category_code2.99                                   -2.118e-10  3.021e+01
## category_code20.81                                  -4.373e-10  1.012e+02
## category_code20.83                                  -2.091e-10  2.124e+01
## category_code212.94                                 -1.957e-10  1.427e+02
## category_code219.88                                 -1.901e-10  1.427e+02
## category_code22.43                                   1.646e-10  1.427e+02
## category_code22.66                                  -2.070e-10  5.161e+01
## category_code222.22                                 -3.891e-10  7.206e+01
## category_code23.13                                  -8.518e-10  3.185e+01
## category_code23.14                                  -1.957e-10  1.427e+02
## category_code23.15                                  -2.090e-10  1.687e+01
## category_code23.33                                  -3.548e-10  1.012e+02
## category_code234.94                                 -1.998e-10  1.427e+02
## category_code24.28                                  -2.024e-10  8.293e+01
## category_code245.93                                 -1.943e-10  1.427e+02
## category_code25.44                                  -2.093e-10  1.012e+02
## category_code25.46                                  -1.852e-10  1.931e+01
## category_code26.62                                  -2.089e-10  3.021e+01
## category_code27.08                                  -2.350e-10  2.928e+01
## category_code27.29                                  -1.910e-10  1.427e+02
## category_code27.34                                  -2.086e-10  1.012e+02
## category_code27.75                                  -2.238e-10  8.293e+01
## category_code27.78                                  -2.093e-10  2.101e+01
## category_code270.67                                 -2.093e-10  1.427e+02
## category_code28.94                                  -2.110e-10  2.242e+01
## category_code29.63                                  -1.815e-10  1.214e+01
## category_code3.45                                   -2.001e-10  2.583e+01
## category_code3.47                                   -2.057e-10  1.535e+01
## category_code3.89                                   -1.762e-10  1.405e+01
## category_code30.09                                  -2.052e-10  1.587e+01
## category_code300.90                                 -1.982e-10  1.427e+02
## category_code31.23                                  -2.101e-10  2.186e+01
## category_code314.79                                 -2.031e-10  1.427e+02
## category_code32.38                                  -2.022e-10  1.012e+02
## category_code33.33                                  -2.110e-10  1.427e+02
## category_code33.54                                  -2.204e-10  3.247e+01
## category_code34.70                                  -2.281e-10  5.921e+01
## category_code34.72                                  -2.185e-10  1.994e+01
## category_code35.39                                  -2.119e-10  5.500e+01
## category_code37.04                                  -1.964e-10  1.772e+01
## category_code370.35                                 -2.917e-10  1.427e+02
## category_code38.17                                  -2.259e-10  4.645e+01
## category_code39.33                                  -2.066e-10  8.293e+01
## category_code39.56                                  -2.737e-10  1.427e+02
## category_code4.14                                   -2.248e-10  2.885e+01
## category_code4.38                                   -2.070e-10  1.427e+02
## category_code4.61                                   -2.708e-10  5.161e+01
## category_code4.63                                   -2.041e-10  1.258e+01
## category_code40.49                                  -1.608e-10  6.466e+01
## category_code41.64                                  -2.168e-10  7.206e+01
## category_code41.67                                  -1.979e-10  2.670e+01
## category_code43.96                                  -2.069e-10  1.427e+02
## category_code46.27                                  -2.626e-10  7.206e+01
## category_code46.30                                  -1.910e-10  4.645e+01
## category_code472.02                                 -3.898e-10  1.427e+02
## category_code486.09                                 -2.090e-10  1.427e+02
## category_code5.30                                   -2.247e-10  1.012e+02
## category_code5.53                                   -2.758e-10  1.012e+02
## category_code5.56                                   -2.217e-10  1.427e+02
## category_code5.79                                   -2.151e-10  1.805e+01
## category_code50.90                                  -2.176e-10  6.466e+01
## category_code50.93                                  -2.205e-10  2.186e+01
## category_code53.22                                  -4.625e-10  1.427e+02
## category_code53.24                                  -2.574e-10  5.161e+01
## category_code532.38                                 -2.080e-10  1.427e+02
## category_code55.53                                  -2.139e-10  1.427e+02
## category_code555.30                                 -9.195e-11  1.427e+02
## category_code555.53                                 -2.247e-10  1.427e+02
## category_code57.87                                  -2.151e-10  1.207e+01
## category_code578.68                                 -1.771e-10  1.427e+02
## category_code6.02                                   -2.111e-10  2.397e+01
## category_code6.71                                   -2.143e-10  5.161e+01
## category_code6.92                                   -2.095e-10  2.227e+01
## category_code6.94                                   -1.522e-10  1.254e+01
## category_code64.79                                  -2.544e-10  8.293e+01
## category_code671.27                                 -2.257e-10  1.427e+02
## category_code69.42                                  -1.948e-10  5.161e+01
## category_code69.44                                  -2.101e-10  1.387e+01
## category_code7.85                                   -2.202e-10  1.427e+02
## category_code729.14                                 -2.309e-10  1.427e+02
## category_code74.07                                  -2.129e-10  8.293e+01
## category_code773.13                                 -1.315e-10  1.427e+02
## category_code78.68                                  -2.258e-10  5.500e+01
## category_code8.08                                   -2.055e-10  1.012e+02
## category_code8.10                                   -2.047e-10  1.207e+01
## category_code8.33                                   -2.276e-10  4.112e+01
## category_code8.54                                   -1.333e-10  8.293e+01
## category_code8.59                                   -3.399e-10  5.921e+01
## category_code8.77                                   -2.151e-10  1.427e+02
## category_code80.76                                  -2.277e-10  8.293e+01
## category_code83.31                                  -2.132e-10  1.427e+02
## category_code83.33                                  -2.138e-10  3.975e+01
## category_code87.94                                  -2.316e-10  1.427e+02
## category_code9.14                                   -2.155e-10  5.921e+01
## category_code9.24                                   -2.139e-10  2.417e+01
## category_code9.26                                   -2.164e-10  1.211e+01
## category_code92.57                                  -2.721e-10  1.012e+02
## category_code92.59                                  -2.186e-10  1.363e+01
## category_code97.20                                  -1.999e-10  8.293e+01
## category_codeaccessories.bag                         1.940e+01  1.400e+01
## category_codeaccessories.umbrella                    7.752e+01  1.012e+02
## category_codeapparel.glove                           2.968e+02  1.696e+01
## category_codeapparel.shirt                           5.758e+01  2.727e+01
## category_codeapparel.sock                                   NA         NA
## category_codeapparel.trousers                        5.345e+01  3.700e+01
## category_codeapparel.tshirt                          4.675e+01  2.435e+01
## category_codeappliances.environment.air_conditioner  2.520e+02  1.273e+01
## category_codeappliances.environment.air_heater       5.803e+01  1.438e+01
## category_codeappliances.environment.climate         -9.435e+01  5.321e+01
## category_codeappliances.environment.fan              4.572e+01  1.366e+01
## category_codeappliances.environment.vacuum           6.162e+01  1.217e+01
## category_codeappliances.environment.water_heater     2.109e+02  1.902e+01
## category_codeappliances.iron                         6.051e+01  1.235e+01
## category_codeappliances.ironing_board                6.850e+01  1.698e+01
## category_codeappliances.kitchen.blender              3.407e+01  1.247e+01
## category_codeappliances.kitchen.coffee_grinder      -3.712e+01  1.657e+01
## category_codeappliances.kitchen.coffee_machine       1.943e+01  1.639e+01
## category_codeappliances.kitchen.dishwasher           3.564e+02  1.417e+01
## category_codeappliances.kitchen.fryer                6.953e+01  3.651e+01
## category_codeappliances.kitchen.grill                1.543e+02  1.565e+01
## category_codeappliances.kitchen.hood                 1.104e+02  1.258e+01
## category_codeappliances.kitchen.juicer               8.284e+01  1.517e+01
## category_codeappliances.kitchen.kettle               2.376e+01  1.212e+01
## category_codeappliances.kitchen.meat_grinder         6.253e+01  1.300e+01
## category_codeappliances.kitchen.microwave            6.954e+01  1.252e+01
## category_codeappliances.kitchen.mixer                1.006e+01  1.333e+01
## category_codeappliances.kitchen.oven                 2.792e+02  1.331e+01
## category_codeappliances.kitchen.refrigerators        4.345e+02  1.227e+01
## category_codeappliances.kitchen.steam_cooker         5.470e+01  2.047e+01
## category_codeappliances.kitchen.toster              -1.295e+01  1.499e+01
## category_codeappliances.kitchen.washer               2.518e+02  1.227e+01
## category_codeappliances.personal.hair_cutter         1.958e+01  1.367e+01
## category_codeappliances.personal.massager            3.709e+01  1.519e+01
## category_codeappliances.personal.scales              2.659e+01  1.248e+01
## category_codeappliances.sewing_machine               8.435e+01  2.516e+01
## category_codeappliances.steam_cleaner                3.974e+01  6.619e+01
## category_codeauto.accessories.alarm                         NA         NA
## category_codeauto.accessories.anti_freeze            3.476e+01  1.176e+02
## category_codeauto.accessories.compressor             1.468e+02  3.973e+01
## category_codeauto.accessories.player                        NA         NA
## category_codeauto.accessories.radar                 -4.329e+01  5.453e+01
## category_codeauto.accessories.videoregister         -2.673e+00  3.530e+01
## category_codecomputers.components.cdrw               3.081e+01  3.382e+01
## category_codecomputers.components.cooler            -1.795e+02  1.595e+01
## category_codecomputers.components.cpu                1.616e+02  1.517e+01
## category_codecomputers.components.hdd                2.694e+01  1.403e+01
## category_codecomputers.components.memory             4.646e+01  2.190e+01
## category_codecomputers.components.motherboard       -1.266e+01  2.867e+01
## category_codecomputers.components.power_supply       9.297e+01  2.470e+01
## category_codecomputers.components.sound_card         9.215e+01  1.544e+02
## category_codecomputers.components.videocards         2.216e+02  2.709e+01
## category_codecomputers.desktop                       2.360e+02  1.881e+01
## category_codecomputers.ebooks                        1.428e+02  5.712e+01
## category_codecomputers.gaming                        2.797e+01  3.460e+01
## category_codecomputers.network.router               -4.634e+01  2.465e+01
## category_codecomputers.notebook                      3.967e+02  1.303e+01
## category_codecomputers.peripherals.camera            4.518e+01  1.868e+01
## category_codecomputers.peripherals.joystick         -1.907e+01  1.673e+01
## category_codecomputers.peripherals.keyboard          1.618e+01  1.382e+01
## category_codecomputers.peripherals.monitor           9.383e+01  1.478e+01
## category_codecomputers.peripherals.mouse            -2.446e+00  1.268e+01
## category_codecomputers.peripherals.printer          -8.406e+01  1.564e+01
## category_codecomputers.peripherals.scanner          -1.608e+02  4.988e+01
## category_codeconstruction.components.faucet          1.441e+01  9.223e+01
## category_codeconstruction.tools.drill               -5.565e+00  3.857e+01
## category_codeconstruction.tools.generator            1.731e+02  9.132e+01
## category_codeconstruction.tools.heater               5.598e+01  1.140e+02
## category_codeconstruction.tools.light                1.517e+01  1.746e+02
## category_codeconstruction.tools.pump                 1.515e+02  9.137e+01
## category_codeconstruction.tools.saw                  4.615e+01  6.499e+01
## category_codeconstruction.tools.screw               -5.423e+01  1.347e+01
## category_codeconstruction.tools.welding              6.674e+01  7.464e+01
## category_codecountry_yard.cultivator                 2.010e+02  9.132e+01
## category_codecountry_yard.lawn_mower                 5.911e+01  5.960e+01
## category_codecountry_yard.watering                  -1.120e+02  1.443e+02
## category_codecountry_yard.weather_station            2.522e+01  6.088e+01
## category_codeelectronics.audio.acoustic              2.167e+02  1.925e+01
## category_codeelectronics.audio.dictaphone           -4.954e+01  1.428e+02
## category_codeelectronics.audio.headphone            -5.644e+01  1.221e+01
## category_codeelectronics.audio.microphone            1.045e+02  1.850e+01
## category_codeelectronics.audio.subwoofer             2.454e+02  1.172e+02
## category_codeelectronics.camera.photo                2.983e+02  3.361e+01
## category_codeelectronics.camera.video                3.280e+02  7.233e+01
## category_codeelectronics.clocks                      5.168e+01  1.339e+01
## category_codeelectronics.smartphone                  1.807e+02  1.198e+01
## category_codeelectronics.tablet                      1.324e+02  1.295e+01
## category_codeelectronics.telephone                  -5.949e+00  1.553e+01
## category_codeelectronics.video.projector             9.213e+01  7.306e+01
## category_codeelectronics.video.tv                    4.031e+02  1.227e+01
## category_codefurniture.bathroom.bath                 8.143e+01  2.733e+01
## category_codefurniture.bathroom.toilet              -7.426e+01  7.560e+01
## category_codefurniture.bedroom.bed                   3.620e+01  1.958e+01
## category_codefurniture.bedroom.blanket               2.677e+02  2.867e+01
## category_codefurniture.bedroom.pillow                1.582e+00  1.940e+01
## category_codefurniture.kitchen.chair                 3.801e+01  1.338e+01
## category_codefurniture.kitchen.table                 2.752e+01  1.221e+01
## category_codefurniture.living_room.cabinet           8.279e+00  1.290e+01
## category_codefurniture.living_room.chair             1.466e+02  3.048e+01
## category_codefurniture.living_room.shelving          2.670e+01  1.358e+01
## category_codefurniture.living_room.sofa              8.304e+01  3.078e+01
## category_codekids.bottles                            2.913e+01  1.464e+02
## category_codekids.carriage                           2.154e+01  2.015e+02
## category_codekids.dolls                              7.823e+01  4.172e+01
## category_codekids.skates                             4.282e+02  2.498e+01
## category_codekids.swing                              1.384e+02  1.464e+02
## category_codekids.toys                               3.326e+01  3.171e+01
## category_codemedicine.tools.tonometer                2.561e+01  1.672e+01
## category_codesport.bicycle                           6.882e+01  5.253e+01
## category_codesport.tennis                           -4.544e+01  4.459e+01
## category_codesport.trainer                           1.794e+02  5.439e+01
## category_codestationery.battery                      1.232e+02  1.867e+01
## category_codestationery.cartrige                    -2.498e+02  1.654e+01
## category_codestationery.paper                       -5.315e+01  1.891e+01
## category_codestationery.stapler                      4.249e+00  4.682e+01
## category_codeUnknown                                 4.154e+01  1.182e+01
##                                                     t value Pr(>|t|)    
## (Intercept)                                          -1.876 0.060687 .  
## brandaccesstyle                                       0.497 0.619145    
## brandaction                                           0.159 0.873898    
## brandadidas                                           0.386 0.699261    
## brandadvantek                                         0.430 0.667544    
## brandaeg                                              8.865  < 2e-16 ***
## brandaerocool                                         1.130 0.258436    
## brandaimoto                                           1.497 0.134517    
## brandairline                                          0.308 0.758102    
## brandakku                                             0.901 0.367395    
## brandaksion                                           1.383 0.166523    
## brandakvafor                                          0.379 0.704899    
## brandalex                                             0.472 0.636759    
## brandalfa                                             0.077 0.938658    
## brandalienware                                       25.256  < 2e-16 ***
## brandalmatv                                           0.200 0.841296    
## brandaltair                                           0.239 0.810732    
## brandaltel                                            4.492 7.06e-06 ***
## brandaltex                                            4.654 3.26e-06 ***
## brandamazon                                           1.202 0.229304    
## brandamd                                              2.763 0.005729 ** 
## brandamigami                                         -0.011 0.991164    
## brandanymode                                          1.332 0.182739    
## brandaoc                                             -6.958 3.46e-12 ***
## brandaoki                                             1.577 0.114848    
## brandapc                                             -4.699 2.61e-06 ***
## brandapollo                                           0.325 0.745257    
## brandapple                                           30.829  < 2e-16 ***
## brandaqua                                            -3.006 0.002645 ** 
## brandaquadent                                         1.062 0.288366    
## brandaquael                                           0.248 0.804460    
## brandaquapick                                         1.823 0.068348 .  
## brandarena                                            0.125 0.900698    
## brandariston                                         -1.826 0.067818 .  
## brandarktika                                          0.845 0.397848    
## brandarnica                                           0.454 0.650054    
## brandart.fit                                          0.447 0.655085    
## brandartberry                                        -0.004 0.997180    
## brandartel                                            2.823 0.004753 ** 
## brandasrock                                           2.597 0.009412 ** 
## brandastonish                                         0.165 0.868688    
## brandasus                                            10.887  < 2e-16 ***
## brandatlant                                          -2.759 0.005795 ** 
## brandatmor                                           -2.744 0.006074 ** 
## brandatom                                             0.143 0.886620    
## brandaudac                                           -0.295 0.767903    
## brandaura                                            -0.025 0.980084    
## brandausini                                           0.320 0.748601    
## brandauthor                                           1.262 0.206907    
## brandava                                              0.372 0.709859    
## brandavermedia                                        1.773 0.076278 .  
## brandavrora                                          -0.042 0.966702    
## brandawax                                            -7.323 2.44e-13 ***
## brandawei                                             2.951 0.003165 ** 
## brandbaboo                                            0.143 0.886620    
## brandbabyliss                                         2.303 0.021261 *  
## brandbaltextile                                       0.971 0.331726    
## brandbarbie                                          -0.200 0.841511    
## brandbardahl                                          0.149 0.881550    
## brandbarjher                                          0.207 0.836016    
## brandbarkan                                           1.797 0.072395 .  
## brandbeats                                            4.901 9.54e-07 ***
## brandbeeline                                          4.056 4.99e-05 ***
## brandbeko                                             2.102 0.035588 *  
## brandbelcando                                        -0.189 0.849806    
## brandbelita                                          -0.147 0.882885    
## brandbelitam                                          0.003 0.997918    
## brandbellissima                                       1.703 0.088538 .  
## brandbequiet                                          3.814 0.000137 ***
## brandberghoff                                         1.197 0.231474    
## brandberkley                                          0.018 0.985553    
## brandberry                                            0.239 0.810732    
## brandbestway                                          0.423 0.672098    
## brandbeurer                                           1.880 0.060079 .  
## brandbfgoodrich                                       0.374 0.708657    
## brandbioderma                                         0.151 0.880118    
## brandbiol                                             0.133 0.894226    
## brandbiolane                                          0.336 0.736550    
## brandbiostar                                          1.155 0.248056    
## brandbirjusa                                         -6.083 1.18e-09 ***
## brandbisfree                                          0.007 0.994576    
## brandblackstar                                        1.750 0.080131 .  
## brandblehk                                            0.294 0.768846    
## brandbloody                                           4.155 3.25e-05 ***
## brandbona                                             2.493 0.012682 *  
## brandborasco                                         -0.053 0.957466    
## brandbork                                            14.174  < 2e-16 ***
## brandborner                                           1.107 0.268509    
## brandbosch                                           11.668  < 2e-16 ***
## brandbose                                             7.008 2.43e-12 ***
## brandbradex                                           0.299 0.764815    
## brandbrateck                                          0.951 0.341815    
## brandbraun                                            4.947 7.54e-07 ***
## brandbrelil                                           0.057 0.954607    
## brandbridgestone                                      1.128 0.259425    
## brandbrother                                          8.633  < 2e-16 ***
## brandbruder                                           0.372 0.709852    
## brandbuebchen                                         0.013 0.989285    
## brandbuff                                             0.146 0.884084    
## brandbushido                                          0.259 0.795337    
## brandbyintek                                          1.688 0.091359 .  
## brandbykski                                           0.521 0.602246    
## brandcablexpert                                       0.061 0.951392    
## brandcalgon                                           0.034 0.972635    
## brandcamelion                                        -3.971 7.15e-05 ***
## brandcannondale                                       6.649 2.96e-11 ***
## brandcanon                                           15.580  < 2e-16 ***
## brandcanyon                                          -3.237 0.001209 ** 
## brandcasada                                           4.043 5.28e-05 ***
## brandcasio                                           -0.585 0.558328    
## brandcaso                                             3.393 0.000692 ***
## brandcaspio                                           1.594 0.110971    
## brandcatrice                                         -0.004 0.996456    
## brandcdc                                              0.154 0.877904    
## brandcelebrat                                         0.667 0.505050    
## brandchicco                                           0.441 0.659121    
## brandchina                                          -16.511  < 2e-16 ***
## brandcilek                                           26.361  < 2e-16 ***
## brandcliny                                           -1.771 0.076535 .  
## brandcollecta                                         0.005 0.995981    
## brandcolorful                                         0.921 0.356823    
## brandcompliment                                      -0.318 0.750260    
## brandcontinent                                       -3.052 0.002274 ** 
## brandcontinental                                      1.451 0.146878    
## brandcoolinar                                         0.787 0.431281    
## brandcort                                             1.587 0.112452    
## brandcougar                                           1.321 0.186636    
## brandcremesso                                         0.324 0.746175    
## brandcullmann                                        -2.950 0.003174 ** 
## brandcyberpower                                      -2.456 0.014031 *  
## brandd-color                                          0.094 0.925059    
## brandd-link                                           2.513 0.011983 *  
## branddaewoo                                           1.467 0.142480    
## branddaikin                                           2.550 0.010768 *  
## branddaiwa                                            0.270 0.787007    
## branddam                                             -0.014 0.988658    
## branddarina                                           2.243 0.024902 *  
## branddc-girls                                        -0.504 0.614208    
## branddecoroom                                         0.403 0.686977    
## branddeepcool                                        -5.631 1.79e-08 ***
## branddeerma                                           0.359 0.719548    
## branddefender                                         0.270 0.787435    
## branddell                                             6.295 3.09e-10 ***
## branddelonghi                                        11.980  < 2e-16 ***
## branddelux                                            3.269 0.001081 ** 
## branddeluxe                                           2.001 0.045428 *  
## branddemidovskiy                                      0.141 0.887893    
## branddepileve                                         0.013 0.989619    
## branddermal                                          -0.021 0.983100    
## branddermoviva                                        0.022 0.982121    
## branddesignskin                                      -0.013 0.989963    
## branddifferent                                       -6.157 7.43e-10 ***
## branddji                                             18.499  < 2e-16 ***
## branddogland                                          2.945 0.003228 ** 
## branddomini                                           1.192 0.233224    
## branddougez                                           0.053 0.957617    
## branddr.beckmann                                     -0.008 0.993405    
## brandduracell                                        -3.049 0.002299 ** 
## branddxracer                                          4.599 4.25e-06 ***
## branddyson                                           22.718  < 2e-16 ***
## brande.gov                                            0.402 0.687576    
## brandecocool                                          1.948 0.051432 .  
## brandecologystone                                     0.928 0.353347    
## brandedifier                                          2.920 0.003499 ** 
## brandeglo                                             0.332 0.739923    
## brandegoiste                                         -0.006 0.995457    
## brandehlektrostandart                                 0.159 0.873898    
## brandehra                                            -3.710 0.000208 ***
## brandelari                                            1.296 0.195052    
## brandelectrolux                                      15.656  < 2e-16 ***
## brandemsa                                             0.905 0.365542    
## brandenergea                                         -0.221 0.825118    
## brandepson                                           14.347  < 2e-16 ***
## brandergolux                                         -5.341 9.25e-08 ***
## brandeset                                           -10.435  < 2e-16 ***
## brandetalon                                          -0.455 0.648897    
## brandeuroprint                                        4.567 4.96e-06 ***
## brandeverlast                                         0.401 0.688349    
## brandeyfel                                           -0.890 0.373427    
## brandezviz                                            0.694 0.487686    
## brandfender                                           2.888 0.003876 ** 
## brandfiltero                                         -0.125 0.900673    
## brandfissman                                          0.879 0.379369    
## brandfitokosmetik                                    -0.012 0.990607    
## brandfixsen                                           0.090 0.928110    
## brandfizan                                            0.092 0.926335    
## brandflama                                            4.175 2.98e-05 ***
## brandfly                                             -1.306 0.191665    
## brandforward                                          1.355 0.175550    
## brandfossil                                           2.555 0.010616 *  
## brandfranke                                           1.310 0.190030    
## brandfujifilm                                         9.853  < 2e-16 ***
## brandgalaxy                                           0.320 0.748809    
## brandgamdias                                          1.175 0.239893    
## brandgamemax                                          1.535 0.124843    
## brandgarmin                                          25.015  < 2e-16 ***
## brandgefest                                          10.742  < 2e-16 ***
## brandgembird                                          0.228 0.819549    
## brandgenau                                            2.566 0.010291 *  
## brandgeneris                                          0.708 0.478865    
## brandgenius                                           1.625 0.104076    
## brandgerat                                            0.231 0.817009    
## brandgewa                                             0.603 0.546524    
## brandgeyzer                                           0.035 0.971841    
## brandgezatone                                         1.843 0.065355 .  
## brandggg                                              0.617 0.537492    
## brandgiant                                            4.563 5.06e-06 ***
## brandgigabyte                                         6.338 2.33e-10 ***
## brandgillette                                         0.077 0.938258    
## brandgiottos                                         -2.058 0.039602 *  
## brandglasslock                                        0.295 0.768226    
## brandglassware                                        0.669 0.503224    
## brandglobal                                           3.344 0.000827 ***
## brandgo-sport                                         5.435 5.49e-08 ***
## brandgolf                                            -0.011 0.991387    
## brandgoodride                                         2.473 0.013411 *  
## brandgoodyear                                        -0.875 0.381483    
## brandgopro                                            5.337 9.48e-08 ***
## brandgorenje                                          3.205 0.001352 ** 
## brandgrans                                            1.522 0.128092    
## brandgreenway                                         3.475 0.000512 ***
## brandgrillver                                         0.433 0.664710    
## brandgrohe                                            9.059  < 2e-16 ***
## brandgtec                                             0.147 0.882904    
## brandgutrend                                          6.945 3.80e-12 ***
## brandhabilead                                         2.185 0.028905 *  
## brandhansa                                           10.733  < 2e-16 ***
## brandhaushalt                                         0.332 0.739803    
## brandhenkel                                           0.077 0.938864    
## brandherschel                                         0.849 0.395636    
## brandhintek                                           0.442 0.658270    
## brandhitachi                                         17.512  < 2e-16 ***
## brandhms                                              0.898 0.369345    
## brandhoco                                            -0.044 0.964515    
## brandhonor                                           -0.514 0.607078    
## brandhotpoint-ariston                                 4.833 1.35e-06 ***
## brandhp                                              14.719  < 2e-16 ***
## brandhtc                                              6.405 1.51e-10 ***
## brandhuawei                                           4.164 3.14e-05 ***
## brandhuion                                           -0.123 0.902067    
## brandhuntkey                                        -10.718  < 2e-16 ***
## brandhurom                                            2.507 0.012162 *  
## brandhuter                                            3.182 0.001466 ** 
## brandhygge                                            4.409 1.04e-05 ***
## brandhyperx                                           6.317 2.68e-10 ***
## brandhyundai                                         -0.367 0.713885    
## brandid-cooling                                       3.489 0.000485 ***
## brandideal                                            0.043 0.965942    
## brandikins                                           -0.003 0.997681    
## brandimetec                                           0.953 0.340431    
## brandincase                                           4.564 5.02e-06 ***
## brandindesit                                         -1.794 0.072806 .  
## brandinhouse                                          0.790 0.429611    
## brandinkax                                            0.676 0.498840    
## brandinoi                                             0.489 0.624819    
## brandinsight                                         -0.699 0.484732    
## brandinspector                                        2.751 0.005940 ** 
## brandintel                                            2.985 0.002835 ** 
## brandintex                                            3.935 8.32e-05 ***
## brandionkini                                          0.136 0.892026    
## brandipower                                         -17.495  < 2e-16 ***
## brandiqos                                             1.013 0.311219    
## brandirbis                                           -3.276 0.001054 ** 
## brandivi                                            -15.563  < 2e-16 ***
## brandivolia                                           0.490 0.624190    
## brandiwalk                                            0.011 0.990987    
## brandjabra                                            1.493 0.135323    
## brandjaguar                                           3.158 0.001587 ** 
## brandjandeks                                          4.630 3.66e-06 ***
## brandjanome                                           4.926 8.42e-07 ***
## brandjbl                                              6.552 5.70e-11 ***
## brandjetair                                          -0.234 0.815273    
## brandjetpik                                           0.530 0.595843    
## brandjoby                                            -4.643 3.44e-06 ***
## brandjoerex                                          -4.233 2.31e-05 ***
## brandjonsbo                                           1.299 0.194052    
## brandjvc                                              0.896 0.370000    
## brandkaabo                                            3.494 0.000475 ***
## brandkama                                             0.377 0.705888    
## brandkarcher                                          5.696 1.23e-08 ***
## brandkaspersky                                       -8.159 3.40e-16 ***
## brandkenko                                           -2.767 0.005650 ** 
## brandkenwood                                          9.209  < 2e-16 ***
## brandkicx                                            -0.744 0.457077    
## brandking                                             2.933 0.003355 ** 
## brandkingston                                         2.017 0.043713 *  
## brandkitchenaid                                      13.983  < 2e-16 ***
## brandkivi                                            -3.669 0.000244 ***
## brandkmk                                              0.019 0.985109    
## brandkomax                                            0.100 0.920640    
## brandkosadaka                                        -0.009 0.992557    
## brandkramet                                          -9.772  < 2e-16 ***
## brandkrups                                           15.212  < 2e-16 ***
## brandkumano                                          -2.492 0.012694 *  
## brandkumho                                            0.395 0.693084    
## brandkurzweil                                         5.123 3.01e-07 ***
## brandkyocera                                          2.824 0.004742 ** 
## brandlamart                                           0.039 0.969103    
## brandlaurastar                                       12.011  < 2e-16 ***
## brandlavazza                                          0.412 0.680657    
## brandlego                                             1.380 0.167735    
## brandlegrand                                         -9.103  < 2e-16 ***
## brandlenovo                                          10.921  < 2e-16 ***
## brandlenspen                                          0.109 0.912845    
## brandlg                                              11.050  < 2e-16 ***
## brandlihom                                            3.463 0.000535 ***
## brandlion                                            -1.355 0.175296    
## brandloewe                                           29.768  < 2e-16 ***
## brandlogitech                                         3.438 0.000586 ***
## brandlol                                             -0.218 0.827179    
## brandlori                                            -0.008 0.993224    
## brandlotte                                            4.478 7.55e-06 ***
## brandlowepro                                          0.474 0.635615    
## brandluch                                            -0.012 0.990329    
## brandlumax                                            0.374 0.708618    
## brandluminarc                                         2.392 0.016760 *  
## brandluxell                                           0.138 0.890015    
## brandmaestro                                          1.027 0.304301    
## brandmakita                                           4.485 7.31e-06 ***
## brandmanfrotto                                       -1.275 0.202292    
## brandmarcato                                          2.438 0.014773 *  
## brandmarcel                                           0.004 0.997139    
## brandmarley                                           1.134 0.256678    
## brandmarshall                                         3.724 0.000196 ***
## brandmart                                             6.722 1.80e-11 ***
## brandmarvel                                           0.385 0.700260    
## brandmatrix                                           0.102 0.918912    
## brandmattel                                           1.587 0.112536    
## brandmaxwell                                          1.219 0.222699    
## brandmcdavid                                          0.097 0.922805    
## brandmedisana                                         0.536 0.591657    
## brandmegogo                                         -17.401  < 2e-16 ***
## brandmercusys                                         2.901 0.003718 ** 
## brandmetabo                                           0.532 0.595071    
## brandmetalions                                        0.164 0.869839    
## brandmichelin                                         0.862 0.388883    
## brandmicro                                           -1.089 0.275992    
## brandmicrolab                                       -10.677  < 2e-16 ***
## brandmicrosoft                                       -8.432  < 2e-16 ***
## brandmidea                                           -5.047 4.50e-07 ***
## brandmilight                                         -0.335 0.737747    
## brandmirage                                           0.304 0.761031    
## brandmisty                                            5.625 1.86e-08 ***
## brandmlife                                            0.095 0.924456    
## brandmonge                                            0.074 0.941100    
## brandmonkart                                          0.185 0.853590    
## brandmoshi                                            4.052 5.09e-05 ***
## brandmotorola                                        -0.391 0.695724    
## brandmoulinex                                         5.395 6.86e-08 ***
## brandmoxom                                            0.146 0.883786    
## brandmsi                                              5.871 4.34e-09 ***
## brandmueller                                          0.004 0.997139    
## brandmujjo                                           -0.340 0.733876    
## brandmuljhtidom                                       0.286 0.774947    
## brandnavien                                           4.978 6.43e-07 ***
## brandnavitel                                          0.825 0.409270    
## brandneo                                              2.216 0.026671 *  
## brandneoline                                          4.856 1.20e-06 ***
## brandneptun                                           0.473 0.636558    
## brandnika                                             0.510 0.609979    
## brandnikon                                           20.542  < 2e-16 ***
## brandninebot                                          2.261 0.023769 *  
## brandnintendo                                         2.367 0.017927 *  
## brandnivea                                            0.005 0.996143    
## brandnokia                                            3.261 0.001111 ** 
## brandnokian                                           0.299 0.764703    
## brandnommi                                            1.578 0.114460    
## brandnone                                             0.827 0.408476    
## brandnordland                                         0.424 0.671221    
## brandnovatrack                                        1.680 0.092895 .  
## brandnuk                                              0.074 0.940989    
## brandnv-print                                         6.611 3.83e-11 ***
## brandnzxt                                             2.537 0.011167 *  
## brandockel                                            0.870 0.384440    
## brandokko                                           -16.703  < 2e-16 ***
## brandokuma                                            0.510 0.609830    
## brandolimpik                                         -0.042 0.966518    
## brandolympus                                          0.579 0.562652    
## brandomron                                            2.045 0.040867 *  
## brandoppo                                             3.306 0.000948 ***
## brandoptoma                                           3.132 0.001738 ** 
## brandoral-b                                          -2.165 0.030368 *  
## brandorgan                                          -18.869  < 2e-16 ***
## brandorico                                           -0.771 0.440954    
## brandosz                                              0.900 0.368206    
## brandowner                                           -0.009 0.992557    
## brandozone                                           -0.535 0.592504    
## brandpaclan                                           0.255 0.798829    
## brandpalisad                                          0.079 0.936804    
## brandpalit                                            1.076 0.282009    
## brandpanasonic                                        5.100 3.40e-07 ***
## brandpaperline                                        0.719 0.472224    
## brandpasabahce                                        0.053 0.957720    
## brandpastel                                           2.035 0.041862 *  
## brandpatriot                                          1.714 0.086613 .  
## brandpccooler                                         2.245 0.024773 *  
## brandpemco                                            0.081 0.935142    
## brandperilla                                          0.418 0.676056    
## brandpeterhof                                         0.660 0.509197    
## brandpetzl                                            0.368 0.712775    
## brandpgytech                                          0.658 0.510650    
## brandphantom                                         -0.580 0.562211    
## brandphilips                                          4.442 8.93e-06 ***
## brandpixel                                            1.335 0.181889    
## brandplantronics                                      2.006 0.044818 *  
## brandplayme                                           2.171 0.029933 *  
## brandplextor                                          0.491 0.623435    
## brandpocketbook                                       1.774 0.076125 .  
## brandpolaris                                          2.281 0.022555 *  
## brandpolaroid                                        -1.627 0.103669    
## brandpolimerbiht                                      0.025 0.979721    
## brandportcase                                         0.399 0.690210    
## brandpowerplant                                      -4.914 8.93e-07 ***
## brandpowertrac                                        0.636 0.524452    
## brandpozis                                           -2.371 0.017736 *  
## brandpresident                                        2.562 0.010395 *  
## brandprestigio                                       -0.382 0.702716    
## brandprocab                                          -0.275 0.783518    
## brandpromtorgservis                                   0.175 0.861209    
## brandproscreen                                        0.790 0.429245    
## brandprovence                                         0.146 0.883990    
## brandpyrex                                            1.209 0.226571    
## brandrapoo                                            2.005 0.044969 *  
## brandrastar                                           1.125 0.260475    
## brandrazer                                            6.315 2.71e-10 ***
## brandredmond                                          2.643 0.008224 ** 
## brandregnum                                           0.788 0.430958    
## brandremington                                        2.275 0.022905 *  
## brandresanta                                          0.775 0.438063    
## brandresto                                            0.392 0.695120    
## brandrioba                                            0.007 0.994576    
## brandritmix                                           0.307 0.758788    
## brandriva                                             0.461 0.644499    
## brandrivacase                                         1.366 0.171880    
## brandroadx                                            0.497 0.619498    
## brandrockstar                                         1.829 0.067373 .  
## brandrondell                                          1.864 0.062377 .  
## brandrosneftjh                                        0.012 0.990677    
## brandrossija                                          0.169 0.865811    
## brandrowenta                                          2.391 0.016796 *  
## brandruggear                                          1.632 0.102783    
## brandsakura                                           2.016 0.043755 *  
## brandsamsonite                                        1.993 0.046294 *  
## brandsamsung                                          7.147 8.90e-13 ***
## brandsamura                                           0.172 0.863733    
## brandsanc                                             4.648 3.35e-06 ***
## brandsaramonic                                        0.077 0.938849    
## brandsatechi                                         -4.259 2.05e-05 ***
## brandsavic                                           -0.068 0.945435    
## brandsbs                                              0.671 0.502110    
## brandscarlett                                         1.490 0.136192    
## brandschwiizer                                        0.126 0.899426    
## brandscreentec                                       -0.047 0.962792    
## brandseagate                                          1.213 0.225118    
## brandseasonic                                         1.432 0.152246    
## brandselect                                          -0.011 0.991220    
## brandsencor                                           2.504 0.012272 *  
## brandsennheiser                                       2.151 0.031467 *  
## brandshelkovica                                       0.078 0.937768    
## brandship                                            10.202  < 2e-16 ***
## brandsibrtekh                                        -1.783 0.074556 .  
## brandsigma                                            0.598 0.549583    
## brandsimax                                            0.599 0.549136    
## brandsimfer                                           2.670 0.007580 ** 
## brandsinger                                           2.656 0.007898 ** 
## brandsjcam                                            1.881 0.060025 .  
## brandskullcandy                                       0.746 0.455927    
## brandsmart                                            0.067 0.946879    
## brandsmeg                                             2.701 0.006906 ** 
## brandsmile                                            3.499 0.000467 ***
## brandsony                                             8.946  < 2e-16 ***
## brandsparta                                           0.004 0.997139    
## brandspiegelau                                        0.568 0.570145    
## brandspigen                                          -0.058 0.953516    
## brandsportop                                          3.213 0.001314 ** 
## brandsports                                          10.928  < 2e-16 ***
## brandstaedtler                                        0.444 0.656685    
## brandstarline                                         4.608 4.07e-06 ***
## brandstatus                                          -5.769 8.00e-09 ***
## brandstaub                                            2.662 0.007778 ** 
## brandsteelseries                                      4.695 2.67e-06 ***
## brandstels                                            1.741 0.081722 .  
## brandsumdex                                           1.519 0.128811    
## brandsuperlux                                        -1.238 0.215752    
## brandsvc                                             -1.679 0.093080 .  
## brandsvetocopy                                        3.100 0.001934 ** 
## brandsynology                                         4.506 6.61e-06 ***
## brandtacx                                             4.534 5.79e-06 ***
## brandtailg                                           11.328  < 2e-16 ***
## brandtamron                                           7.864 3.76e-15 ***
## brandtaoran                                           0.746 0.455520    
## brandtayfun                                          -7.308 2.72e-13 ***
## brandtcl                                             -5.639 1.71e-08 ***
## brandtechnodom                                        0.561 0.574559    
## brandtechnogym                                       28.497  < 2e-16 ***
## brandtechnomax                                        0.995 0.319980    
## brandtefal                                            4.372 1.23e-05 ***
## brandtemdan                                          -0.037 0.970143    
## brandtenda                                            0.046 0.963619    
## brandthefaceshop                                      0.209 0.834644    
## brandthermaltake                                      4.817 1.46e-06 ***
## brandthermex                                         -2.618 0.008859 ** 
## brandthomas                                           7.479 7.54e-14 ***
## brandthule                                            0.611 0.541093    
## brandtigar                                            0.611 0.541093    
## brandtigernu                                          0.304 0.761031    
## brandtimberk                                          0.434 0.664060    
## brandtimson                                           1.296 0.195063    
## brandtion                                             4.070 4.71e-05 ***
## brandtoday                                           -0.003 0.997681    
## brandtopperr                                         -0.304 0.760748    
## brandtornado                                         -0.890 0.373479    
## brandtoro                                             0.088 0.930081    
## brandtoshiba                                          0.501 0.616257    
## brandtoyo                                             0.768 0.442754    
## brandtp-link                                          4.185 2.85e-05 ***
## brandtramp                                           -0.010 0.992047    
## brandtranscend                                        2.095 0.036161 *  
## brandtribe                                           -1.007 0.313911    
## brandtrio                                           -16.206  < 2e-16 ***
## brandtrust                                           -5.304 1.13e-07 ***
## brandtucano                                           1.553 0.120488    
## brandturbo                                           -0.019 0.985035    
## brandtvs                                              2.602 0.009267 ** 
## brandtyr                                              0.167 0.867522    
## brandubisoft                                          0.438 0.661041    
## brandUnknown                                          2.266 0.023465 *  
## brandurbanears                                        1.112 0.266082    
## branduriage                                           0.077 0.938656    
## brandusams                                            1.499 0.133927    
## branduteki                                          -14.336  < 2e-16 ***
## brandvarta                                           -3.379 0.000727 ***
## brandventa                                            2.753 0.005899 ** 
## brandviatti                                           0.819 0.412843    
## brandvictoria                                         1.649 0.099073 .  
## brandvikhrjh                                          1.973 0.048474 *  
## brandvirtuix                                          0.086 0.931495    
## brandvitehks                                         -0.093 0.926240    
## brandvitek                                            1.612 0.106995    
## brandvivo                                             1.179 0.238554    
## brandvoin                                            -0.573 0.566774    
## brandvortex                                           0.326 0.744793    
## brandwacom                                            1.693 0.090466 .  
## brandweber                                            0.198 0.843245    
## brandwethepeople                                      2.998 0.002714 ** 
## brandwhirlpool                                        9.329  < 2e-16 ***
## brandwilmax                                           0.524 0.600265    
## brandwilson                                           0.076 0.939212    
## brandwintek                                           0.554 0.579816    
## brandwmf                                              4.585 4.55e-06 ***
## brandwonlex                                           0.185 0.853437    
## brandwxd                                              0.303 0.761906    
## brandx-game                                           2.421 0.015463 *  
## brandxbox                                             3.836 0.000125 ***
## brandxerox                                            3.802 0.000144 ***
## brandxiaomi                                           2.795 0.005197 ** 
## brandxp-pen                                           1.725 0.084567 .  
## brandyokohama                                         0.989 0.322749    
## brandyonker                                           0.450 0.652988    
## brandyoobao                                           1.649 0.099114 .  
## brandzala                                             1.260 0.207637    
## brandzalman                                           0.689 0.491092    
## brandzeppelin                                         0.130 0.896752    
## brandzhiyun                                           4.648 3.35e-06 ***
## brandzhorka                                          -0.012 0.990720    
## brandzowie                                            3.182 0.001465 ** 
## brandzugo                                             0.381 0.703328    
## brandzwilling                                         2.191 0.028440 *  
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## category_code19.49                                    0.000 1.000000    
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## category_code2.29                                     0.000 1.000000    
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## category_code2.99                                     0.000 1.000000    
## category_code20.81                                    0.000 1.000000    
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## category_code3.45                                     0.000 1.000000    
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## category_code4.14                                     0.000 1.000000    
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## category_code40.49                                    0.000 1.000000    
## category_code41.64                                    0.000 1.000000    
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## category_code43.96                                    0.000 1.000000    
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## category_code46.30                                    0.000 1.000000    
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## category_code486.09                                   0.000 1.000000    
## category_code5.30                                     0.000 1.000000    
## category_code5.53                                     0.000 1.000000    
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## category_code50.90                                    0.000 1.000000    
## category_code50.93                                    0.000 1.000000    
## category_code53.22                                    0.000 1.000000    
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## category_code6.02                                     0.000 1.000000    
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## category_code7.85                                     0.000 1.000000    
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## category_code74.07                                    0.000 1.000000    
## category_code773.13                                   0.000 1.000000    
## category_code78.68                                    0.000 1.000000    
## category_code8.08                                     0.000 1.000000    
## category_code8.10                                     0.000 1.000000    
## category_code8.33                                     0.000 1.000000    
## category_code8.54                                     0.000 1.000000    
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## category_code87.94                                    0.000 1.000000    
## category_code9.14                                     0.000 1.000000    
## category_code9.24                                     0.000 1.000000    
## category_code9.26                                     0.000 1.000000    
## category_code92.57                                    0.000 1.000000    
## category_code92.59                                    0.000 1.000000    
## category_code97.20                                    0.000 1.000000    
## category_codeaccessories.bag                          1.386 0.165757    
## category_codeaccessories.umbrella                     0.766 0.443821    
## category_codeapparel.glove                           17.496  < 2e-16 ***
## category_codeapparel.shirt                            2.111 0.034757 *  
## category_codeapparel.sock                                NA       NA    
## category_codeapparel.trousers                         1.445 0.148518    
## category_codeapparel.tshirt                           1.919 0.054928 .  
## category_codeappliances.environment.air_conditioner  19.798  < 2e-16 ***
## category_codeappliances.environment.air_heater        4.037 5.43e-05 ***
## category_codeappliances.environment.climate          -1.773 0.076196 .  
## category_codeappliances.environment.fan               3.346 0.000819 ***
## category_codeappliances.environment.vacuum            5.064 4.12e-07 ***
## category_codeappliances.environment.water_heater     11.085  < 2e-16 ***
## category_codeappliances.iron                          4.898 9.69e-07 ***
## category_codeappliances.ironing_board                 4.034 5.49e-05 ***
## category_codeappliances.kitchen.blender               2.732 0.006295 ** 
## category_codeappliances.kitchen.coffee_grinder       -2.240 0.025081 *  
## category_codeappliances.kitchen.coffee_machine        1.186 0.235631    
## category_codeappliances.kitchen.dishwasher           25.142  < 2e-16 ***
## category_codeappliances.kitchen.fryer                 1.905 0.056847 .  
## category_codeappliances.kitchen.grill                 9.859  < 2e-16 ***
## category_codeappliances.kitchen.hood                  8.781  < 2e-16 ***
## category_codeappliances.kitchen.juicer                5.460 4.78e-08 ***
## category_codeappliances.kitchen.kettle                1.961 0.049900 *  
## category_codeappliances.kitchen.meat_grinder          4.810 1.51e-06 ***
## category_codeappliances.kitchen.microwave             5.556 2.76e-08 ***
## category_codeappliances.kitchen.mixer                 0.755 0.450298    
## category_codeappliances.kitchen.oven                 20.983  < 2e-16 ***
## category_codeappliances.kitchen.refrigerators        35.402  < 2e-16 ***
## category_codeappliances.kitchen.steam_cooker          2.672 0.007538 ** 
## category_codeappliances.kitchen.toster               -0.864 0.387710    
## category_codeappliances.kitchen.washer               20.527  < 2e-16 ***
## category_codeappliances.personal.hair_cutter          1.432 0.152005    
## category_codeappliances.personal.massager             2.442 0.014601 *  
## category_codeappliances.personal.scales               2.131 0.033080 *  
## category_codeappliances.sewing_machine                3.352 0.000801 ***
## category_codeappliances.steam_cleaner                 0.600 0.548227    
## category_codeauto.accessories.alarm                      NA       NA    
## category_codeauto.accessories.anti_freeze             0.296 0.767581    
## category_codeauto.accessories.compressor              3.696 0.000219 ***
## category_codeauto.accessories.player                     NA       NA    
## category_codeauto.accessories.radar                  -0.794 0.427280    
## category_codeauto.accessories.videoregister          -0.076 0.939657    
## category_codecomputers.components.cdrw                0.911 0.362302    
## category_codecomputers.components.cooler            -11.258  < 2e-16 ***
## category_codecomputers.components.cpu                10.652  < 2e-16 ***
## category_codecomputers.components.hdd                 1.921 0.054765 .  
## category_codecomputers.components.memory              2.122 0.033869 *  
## category_codecomputers.components.motherboard        -0.442 0.658831    
## category_codecomputers.components.power_supply        3.765 0.000167 ***
## category_codecomputers.components.sound_card          0.597 0.550705    
## category_codecomputers.components.videocards          8.180 2.87e-16 ***
## category_codecomputers.desktop                       12.546  < 2e-16 ***
## category_codecomputers.ebooks                         2.500 0.012434 *  
## category_codecomputers.gaming                         0.808 0.418840    
## category_codecomputers.network.router                -1.880 0.060136 .  
## category_codecomputers.notebook                      30.453  < 2e-16 ***
## category_codecomputers.peripherals.camera             2.419 0.015573 *  
## category_codecomputers.peripherals.joystick          -1.140 0.254338    
## category_codecomputers.peripherals.keyboard           1.171 0.241568    
## category_codecomputers.peripherals.monitor            6.350 2.17e-10 ***
## category_codecomputers.peripherals.mouse             -0.193 0.847027    
## category_codecomputers.peripherals.printer           -5.374 7.72e-08 ***
## category_codecomputers.peripherals.scanner           -3.224 0.001266 ** 
## category_codeconstruction.components.faucet           0.156 0.875816    
## category_codeconstruction.tools.drill                -0.144 0.885275    
## category_codeconstruction.tools.generator             1.895 0.058077 .  
## category_codeconstruction.tools.heater                0.491 0.623515    
## category_codeconstruction.tools.light                 0.087 0.930777    
## category_codeconstruction.tools.pump                  1.658 0.097230 .  
## category_codeconstruction.tools.saw                   0.710 0.477642    
## category_codeconstruction.tools.screw                -4.027 5.64e-05 ***
## category_codeconstruction.tools.welding               0.894 0.371199    
## category_codecountry_yard.cultivator                  2.201 0.027737 *  
## category_codecountry_yard.lawn_mower                  0.992 0.321283    
## category_codecountry_yard.watering                   -0.776 0.437677    
## category_codecountry_yard.weather_station             0.414 0.678707    
## category_codeelectronics.audio.acoustic              11.260  < 2e-16 ***
## category_codeelectronics.audio.dictaphone            -0.347 0.728616    
## category_codeelectronics.audio.headphone             -4.624 3.77e-06 ***
## category_codeelectronics.audio.microphone             5.647 1.64e-08 ***
## category_codeelectronics.audio.subwoofer              2.094 0.036237 *  
## category_codeelectronics.camera.photo                 8.874  < 2e-16 ***
## category_codeelectronics.camera.video                 4.535 5.77e-06 ***
## category_codeelectronics.clocks                       3.859 0.000114 ***
## category_codeelectronics.smartphone                  15.087  < 2e-16 ***
## category_codeelectronics.tablet                      10.224  < 2e-16 ***
## category_codeelectronics.telephone                   -0.383 0.701573    
## category_codeelectronics.video.projector              1.261 0.207300    
## category_codeelectronics.video.tv                    32.850  < 2e-16 ***
## category_codefurniture.bathroom.bath                  2.980 0.002885 ** 
## category_codefurniture.bathroom.toilet               -0.982 0.326000    
## category_codefurniture.bedroom.bed                    1.849 0.064516 .  
## category_codefurniture.bedroom.blanket                9.339  < 2e-16 ***
## category_codefurniture.bedroom.pillow                 0.082 0.935020    
## category_codefurniture.kitchen.chair                  2.840 0.004514 ** 
## category_codefurniture.kitchen.table                  2.253 0.024243 *  
## category_codefurniture.living_room.cabinet            0.642 0.521019    
## category_codefurniture.living_room.chair              4.811 1.51e-06 ***
## category_codefurniture.living_room.shelving           1.965 0.049366 *  
## category_codefurniture.living_room.sofa               2.697 0.006989 ** 
## category_codekids.bottles                             0.199 0.842217    
## category_codekids.carriage                            0.107 0.914859    
## category_codekids.dolls                               1.875 0.060812 .  
## category_codekids.skates                             17.142  < 2e-16 ***
## category_codekids.swing                               0.946 0.344371    
## category_codekids.toys                                1.049 0.294225    
## category_codemedicine.tools.tonometer                 1.532 0.125641    
## category_codesport.bicycle                            1.310 0.190134    
## category_codesport.tennis                            -1.019 0.308228    
## category_codesport.trainer                            3.299 0.000971 ***
## category_codestationery.battery                       6.601 4.11e-11 ***
## category_codestationery.cartrige                    -15.107  < 2e-16 ***
## category_codestationery.paper                        -2.810 0.004956 ** 
## category_codestationery.stapler                       0.091 0.927694    
## category_codeUnknown                                  3.515 0.000439 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 142.2 on 117421 degrees of freedom
## Multiple R-squared:  0.6043, Adjusted R-squared:  0.6015 
## F-statistic:   211 on 850 and 117421 DF,  p-value: < 2.2e-16

Interpretation

A Multiple Linear Regression model was developed using brand and category_code as predictor variables to estimate product price. By incorporating multiple predictors, the model aims to explain more variation in product price and improve prediction accuracy compared with the Simple Linear Regression model.

5.6 Model Evaluation

#----------#
# Simple Model
#----------#

pred_simple <- predict(
  simple_model,
  newdata = test_data
)

valid_simple <- !is.na(pred_simple)

RMSE_simple <- sqrt(
  mean((test_data$price[valid_simple] -
          pred_simple[valid_simple])^2)
)

MAE_simple <- mean(
  abs(test_data$price[valid_simple] -
        pred_simple[valid_simple])
)

R2_simple <- 1 -
  sum((test_data$price[valid_simple] -
         pred_simple[valid_simple])^2) /
  sum((test_data$price[valid_simple] -
         mean(test_data$price[valid_simple]))^2)


#----------#
# Multiple Model
#----------#

pred_multiple <- predict(
  multiple_model,
  newdata = test_data
)

valid_multiple <- !is.na(pred_multiple)

RMSE_multiple <- sqrt(
  mean((test_data$price[valid_multiple] -
          pred_multiple[valid_multiple])^2)
)

MAE_multiple <- mean(
  abs(test_data$price[valid_multiple] -
        pred_multiple[valid_multiple])
)

R2_multiple <- 1 -
  sum((test_data$price[valid_multiple] -
         pred_multiple[valid_multiple])^2) /
  sum((test_data$price[valid_multiple] -
         mean(test_data$price[valid_multiple]))^2)


#----------#
# Comparison Table
#----------#

results <- data.frame(
  Model = c("Simple Linear Regression",
            "Multiple Linear Regression"),
  RMSE = c(RMSE_simple,
           RMSE_multiple),
  MAE = c(MAE_simple,
          MAE_multiple),
  R2 = c(R2_simple,
         R2_multiple)
)

results

Interpretation

The model evaluation results show that the Multiple Linear Regression model outperformed the Simple Linear Regression model. The Multiple Linear Regression model achieved a lower RMSE (141.05 vs. 162.16) and lower MAE (63.15 vs. 77.31), indicating smaller prediction errors. It also obtained a higher R² value (0.6067 vs. 0.4801), meaning it explains approximately 60.67% of the variation in product price compared to 48.01% for the Simple Linear Regression model. Therefore, the Multiple Linear Regression model was selected as the final model because it provides better predictive performance and explanatory power.

5.7 Regression Diagnostic Plots

Diagnostic plots were generated to evaluate regression assumptions and model performance.

par(mfrow = c(2, 2))
plot(multiple_model)

par(mfrow = c(1, 1))

Interpretation

The diagnostic plots reveal patterns typical of right-skewed price data: residuals fan out at higher fitted values (heteroscedasticity) and the Q-Q plot departs from the line in the upper tail, driven by premium-priced outliers. The model remains useful for typical price ranges, but a log transformation of price would be a natural refinement if more precise prediction of expensive items were required.

5.8 Regression Modelling Summary

This study applied regression modelling techniques to predict product prices in e-commerce transactions. The findings showed that brand and product category significantly influence product price. Multiple linear regression produced better predictive performance than simple regression, indicating that combining multiple predictors improves price estimation accuracy.


6.0 Interpretation and Conclusion

This project set out to explore, clean, and model a large-scale e-commerce purchase history dataset, and all four objectives were met.

Data quality. The raw dataset contained duplicates and substantial missing values in category_code, brand, and user_id. These were resolved through deduplication and “Unknown” placeholders, retaining the full transaction history rather than discarding incomplete records.

Customer behaviour. EDA showed that transaction volume is concentrated in a small number of brands and categories, prices are heavily right-skewed, and purchasing activity follows clear hourly, weekly, and monthly rhythms. These patterns informed every modelling decision that followed.

Classification. Logistic Regression was the strongest classifier of high-value vs low-value purchases (ROC ≈ 0.91), with Random Forest a close second and Naive Bayes unusable due to its collapse into the majority class. Product category and brand were the dominant predictors, with temporal features adding modest value.

Regression. The multiple linear regression using brand and category explained roughly 60% of price variation, a substantial improvement over the brand-only baseline. The diagnostic plots suggest a log-price model as the most promising next step.

Practical implication. For an electronics retailer, the results point to a clear strategy: high-value purchases are driven primarily by what is bought (category) and from whom (premium brands such as Apple and Samsung), more than when. Marketing spend aimed at high-value customers should therefore target category and brand affinity first, with timing as a secondary lever.