Program_11

Author

Anusha Y K

###Program: Write an R program to generate a basic box plot, enhanced with notches and outlines, and grouped by a categorical variable, using ggplot2.

STEP :1 Load Required Package

We use ggplot2 package for DV.

#Load the ggplot2 package
library(ggplot2)

STEP :2 Use an Inbuilt Dataset

we use inbuilt data set iris.It contains measurements of sepal and petal dimensions for 3 species of iris flowers.

Setosa
Versicolor
Virginica

data(iris)
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

str(iris)

'data.frame':   150 obs. of  5 variables:
 $ Sepal.Length: num  5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
 $ Sepal.Width : num  3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
 $ Petal.Length: num  1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ...
 $ Petal.Width : num  0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ...
 $ Species     : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ...

The speciescolumn is categorical, making it suitable for grouping, while Sepal.Lengthis a numerical variable we’ll have to analyze.

STEP :3 Create a Notches box plot grouped by Species.

now create a box plot for Sepal.Length,grouped by Species, we’ll enhance the plot using:- Notches to show the confidence interval around the median - Outliers Highlighting using color and shape - Aesthetic enhancement like fill color and theme.

ggplot(iris, aes(x = Species, y = Sepal.Length, fill = Species)) +
  geom_boxplot(
    notch = TRUE, 
    notchwidth = 0.6,
    outlier.colour = "red",     
    outlier.shape = 16,
    fill = "cyan",
    alpha = 0.7
  ) +
  labs(
    title = "Sepal Length Distribution by Iris Species",
    subtitle = "Box Plot with Notches and Outliers Highlighting",
    x = "Species",
     y = "Sepal Length"
  ) +
  theme_minimal()

Box Plot -Each box summarises the distribution of the Sepal.Lenghtfor a species - showing the interquartile range(IQR) ,median and potential outliers.

Notches -The notches. give a rough 95% confidence interval around the median.If notches of two boxes do not overlap, the medians are significantly different.

Outliers -Points that fall outside 1.5 IQR from the quartiles are considered outliers and shown in red.

Grouping -The plot groups values based on the categorical variable Species , Helping compare between groups.

Aesthetics -theme_minimal()provides a clean background, while colors and transparency make the plot readable.