Program 4

Develop a script in R to produce a bar graph displaying the frequency distribution of categorical data in a given dataset, grouped by a specific variable, using ggplot2.

Step 1: Load the necessary libraries

library(ggplot2)

Step 2: Load the dataset

# Load dataset
data <- mtcars

# Display first few rows
head(data)

                   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

Step 3: Convert numerical data to categorical data

data$cyl <- as.factor(data$cyl)
data$gear <- as.factor(data$gear)

Step 4: Create a bar graph

# Create a bar graph
ggplot(data, aes(x = cyl, fill = gear)) +
  geom_bar(position = "dodge") +  # Grouped bar chart
  labs(title = "Frequency of Cylinders Grouped by Gear Type ",
       x = "Number of Cylinders",
       y = "Count",
       fill = "Gears") +  # Legend title
  theme_minimal()

Explanation of the Plot

X-Axis (cyl)

• Displays cylinder categories (4, 6, 8 cylinders).

Y-Axis (Frequency Count)

• Represents the number of cars in each category.

Color Fill (gear)

• Differentiates cars based on number of gears (3, 4, 5 gears).

Grouped Bars (position = "dodge")

• Ensures bars are side by side instead of stacked.

Minimal Theme (theme_minimal())

• Provides a clean and readable layout.