Cleaning and Preparing Data

Load Required Packages

install.packages("tidyverse")
## Installing package into '/cloud/lib/x86_64-pc-linux-gnu-library/4.5'
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install.packages("dplyr")
## Installing package into '/cloud/lib/x86_64-pc-linux-gnu-library/4.5'
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library(tidyverse)
## ── Attaching core tidyverse packages ──────────────────────── tidyverse 2.0.0 ──
## ✔ dplyr     1.1.4     ✔ readr     2.1.6
## ✔ forcats   1.0.1     ✔ stringr   1.6.0
## ✔ ggplot2   4.0.1     ✔ tibble    3.3.0
## ✔ lubridate 1.9.4     ✔ tidyr     1.3.2
## ✔ purrr     1.2.0
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## ✖ dplyr::lag()    masks stats::lag()
## ℹ Use the conflicted package (<http://conflicted.r-lib.org/>) to force all conflicts to become errors
library(dplyr)

Load the Dataset

read_builtin("mtcars")
##                      mpg cyl  disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4           21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag       21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710          22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive      21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout   18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
## Valiant             18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
## Duster 360          14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4
## Merc 240D           24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2
## Merc 230            22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2
## Merc 280            19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
## Merc 280C           17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
## Merc 450SE          16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
## Merc 450SL          17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
## Merc 450SLC         15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3
## Cadillac Fleetwood  10.4   8 472.0 205 2.93 5.250 17.98  0  0    3    4
## Lincoln Continental 10.4   8 460.0 215 3.00 5.424 17.82  0  0    3    4
## Chrysler Imperial   14.7   8 440.0 230 3.23 5.345 17.42  0  0    3    4
## Fiat 128            32.4   4  78.7  66 4.08 2.200 19.47  1  1    4    1
## Honda Civic         30.4   4  75.7  52 4.93 1.615 18.52  1  1    4    2
## Toyota Corolla      33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1
## Toyota Corona       21.5   4 120.1  97 3.70 2.465 20.01  1  0    3    1
## Dodge Challenger    15.5   8 318.0 150 2.76 3.520 16.87  0  0    3    2
## AMC Javelin         15.2   8 304.0 150 3.15 3.435 17.30  0  0    3    2
## Camaro Z28          13.3   8 350.0 245 3.73 3.840 15.41  0  0    3    4
## Pontiac Firebird    19.2   8 400.0 175 3.08 3.845 17.05  0  0    3    2
## Fiat X1-9           27.3   4  79.0  66 4.08 1.935 18.90  1  1    4    1
## Porsche 914-2       26.0   4 120.3  91 4.43 2.140 16.70  0  1    5    2
## Lotus Europa        30.4   4  95.1 113 3.77 1.513 16.90  1  1    5    2
## Ford Pantera L      15.8   8 351.0 264 4.22 3.170 14.50  0  1    5    4
## Ferrari Dino        19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6
## Maserati Bora       15.0   8 301.0 335 3.54 3.570 14.60  0  1    5    8
## Volvo 142E          21.4   4 121.0 109 4.11 2.780 18.60  1  1    4    2
head(mtcars)
##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

Inspecting the Data

str(mtcars)
## 'data.frame':    32 obs. of  11 variables:
##  $ mpg : num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
##  $ cyl : num  6 6 4 6 8 6 8 4 4 6 ...
##  $ disp: num  160 160 108 258 360 ...
##  $ hp  : num  110 110 93 110 175 105 245 62 95 123 ...
##  $ drat: num  3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
##  $ wt  : num  2.62 2.88 2.32 3.21 3.44 ...
##  $ qsec: num  16.5 17 18.6 19.4 17 ...
##  $ vs  : num  0 0 1 1 0 1 0 1 1 1 ...
##  $ am  : num  1 1 1 0 0 0 0 0 0 0 ...
##  $ gear: num  4 4 4 3 3 3 3 4 4 4 ...
##  $ carb: num  4 4 1 1 2 1 4 2 2 4 ...

What does each row represent?

  • The rows represent different things associated with each car

Name two variables that are numeric.

  • mpg and wt

Name one variable that represents a category, even if it is currently stored as a number.

  • cyl is what type of cylinder the car is which is a category represented by a number

Cleaning the Data

Convert Variables to Factors

mtcars= mtcars %>%
  mutate(cyl=factor(cyl), am=factor(am))
str(mtcars)
## 'data.frame':    32 obs. of  11 variables:
##  $ mpg : num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
##  $ cyl : Factor w/ 3 levels "4","6","8": 2 2 1 2 3 2 3 1 1 2 ...
##  $ disp: num  160 160 108 258 360 ...
##  $ hp  : num  110 110 93 110 175 105 245 62 95 123 ...
##  $ drat: num  3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
##  $ wt  : num  2.62 2.88 2.32 3.21 3.44 ...
##  $ qsec: num  16.5 17 18.6 19.4 17 ...
##  $ vs  : num  0 0 1 1 0 1 0 1 1 1 ...
##  $ am  : Factor w/ 2 levels "0","1": 2 2 2 1 1 1 1 1 1 1 ...
##  $ gear: num  4 4 4 3 3 3 3 4 4 4 ...
##  $ carb: num  4 4 1 1 2 1 4 2 2 4 ...

Selecting Relevant Variables

clean_cars=mtcars %>%
  select(mpg,hp,wt,cyl,am)
head(clean_cars)
##                    mpg  hp    wt cyl am
## Mazda RX4         21.0 110 2.620   6  1
## Mazda RX4 Wag     21.0 110 2.875   6  1
## Datsun 710        22.8  93 2.320   4  1
## Hornet 4 Drive    21.4 110 3.215   6  0
## Hornet Sportabout 18.7 175 3.440   8  0
## Valiant           18.1 105 3.460   6  0

Filtering Observations

car_hp= clean_cars %>%
  filter(hp > 100)
nrow(car_hp)
## [1] 23

Creating New Variables

car_hp= car_hp %>%
  mutate("power_to_weight"= hp/wt)
head(car_hp)
##                    mpg  hp    wt cyl am power_to_weight
## Mazda RX4         21.0 110 2.620   6  1        41.98473
## Mazda RX4 Wag     21.0 110 2.875   6  1        38.26087
## Hornet 4 Drive    21.4 110 3.215   6  0        34.21462
## Hornet Sportabout 18.7 175 3.440   8  0        50.87209
## Valiant           18.1 105 3.460   6  0        30.34682
## Duster 360        14.3 245 3.570   8  0        68.62745

Grouping and Summarizing Data

Summary by Number of Cylinders

summary_cyl= car_hp %>%
  group_by(cyl) %>%
  summarize(
     mean_mpg= mean(mpg),
     mean_power_to_weight= mean(power_to_weight),
     n = n())
summary_cyl
## # A tibble: 3 × 4
##   cyl   mean_mpg mean_power_to_weight     n
##   <fct>    <dbl>                <dbl> <int>
## 1 4         25.9                 56.9     2
## 2 6         19.7                 39.9     7
## 3 8         15.1                 53.9    14

Summary by Transmission Type

summary_transmission= car_hp %>%
  group_by(am) %>%
  summarize(
    mean_mpg= mean(mpg),
    mean_power_to_weight= mean(power_to_weight)
  )
summary_transmission
## # A tibble: 2 × 3
##   am    mean_mpg mean_power_to_weight
##   <fct>    <dbl>                <dbl>
## 1 0         16.1                 44.6
## 2 1         20.6                 62.1

Interpreting the Summaries

Which group appears to have higher fuel efficiency?

  • The 4 cylinder car seems to have the highest fuel efficiency

Which summary table would be useful for making a bar plot?

  • I think that the cylinder table would do better with a bar plot since it is comparing the means across three categories.

Which would work better for a box plot later?

  • The transmission table would work better for a box plot

Reflection

One thing that was confusing to me was remembering the code set up for the proper summary tables. The mutate function makes more sense to me now since I have used it more. The first part tidying the data when renaming or telling it to pull the data from also makes more sense. I was struggling with understand what it meant but basically the first part creates the name or new name and then = to the data set you want to pull from or edit. Cleaning and summarizing the data before plotting is important because it helps you get specific information from the data that you want instead of extra stuff. Cleaning the data also helps me undertand what all of the data represents making it easier to analyze.