PROGRAM 9

Author

JAGADISH J M

Objective

Create multiple histograms using ggplot2::facet_wrap() to visualize how a variable (e.g., Sepal.Length) is distributed across different groups (e.g., Species) in a built-in R dataset.

Requirements

Before proceeding, make sure you have the ggplot2 package installed. You can install it using: install.packages(“ggplot2”) Then, load the package:

# Load the ggplot2 package
library(ggplot2)

Step 1: Load and Explore the Dataset

We’ll use the built-in iris dataset. This dataset contains:

150 rows (observations)
4 numeric columns: Sepal.Length, Sepal.Width, Petal.Length, Petal.Width
1 categorical column: Species (Setosa, Versicolor, Virginica)

Let’s view the first few rows.

# Load the iris dataset
data(iris)

# View the first few rows of the dataset
head(iris)

  Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1          5.1         3.5          1.4         0.2  setosa
2          4.9         3.0          1.4         0.2  setosa
3          4.7         3.2          1.3         0.2  setosa
4          4.6         3.1          1.5         0.2  setosa
5          5.0         3.6          1.4         0.2  setosa
6          5.4         3.9          1.7         0.4  setosa

Step 2: Create Grouped Histograms Using facet_wrap

Let’s now create histograms of Sepal.Length for each Species using ggplot2 and facet_wrap().

# Create histograms using facet_wrap for grouped data
ggplot(iris, aes(x = Sepal.Length)) +
  geom_histogram(binwidth = 0.3, fill = "skyblue", color = "black") +
  facet_wrap(~ Species) +
  labs(title = "Distribution of Sepal Length by Species",
       x = "Sepal Length (cm)",
       y = "Frequency") +
  theme_minimal()

Step 3: Explanation of Each Line

Code Line	Description
`ggplot(iris, aes(x = Sepal.Length))`	Initializes a plot using the `iris` dataset and maps `Sepal.Length` to the x-axis.
`geom_histogram(binwidth = 0.3, ...)`	Adds a histogram layer with a bin width of 0.3.
`fill = "skyblue"`	Sets the fill color of the bars.
`color = "black"`	Sets the border color of the bars.
`facet_wrap(~ Species)`	Creates separate histograms for each species in a grid layout.
`labs(...)`	Adds a title and axis labels.
`theme_minimal()`	Applies a minimal theme for better visualization.

Step 3: Explanation of Each Line

Code Line	Description
`ggplot(iris, aes(x = Sepal.Length))`	Initializes a plot using the `iris` dataset and maps `Sepal.Length` to the x-axis.
`geom_histogram(binwidth = 0.3, ...)`	Adds a histogram layer with a bin width of 0.3.
`fill = "skyblue"`	Sets the fill color of the bars.
`color = "black"`	Sets the border color of the bars.
`facet_wrap(~ Species)`	Creates separate histograms for each species in a grid layout.
`labs(...)`	Adds a title and axis labels.
`theme_minimal()`	Applies a minimal theme for better visualization.