How to plot violin plot in R?
This recipe helps you plot violin plot in R
Recipe Objective
Violin plots are similar to boxplots which showcases the probability density along with interquartile, median and range at different values. They are more informative than boxplots which are used to showcase the full distribution of the data. They are also known to combine the features of histogram and boxplots. They are mainly used to compare the distribution of different variables/columns in the dataset.
In this recipe we are going to use ggplot2 package to plot the required violin plot. ggplot2 package is based on the book Grammar of Graphics by Wilkinson. This package provides flexibility while incorporating different themes and plot specification with a high level of abstraction. The package mainly uses aesthetic mapping and geometric objects as arguments. Different types of geometric objects include:
- geom_point() - for plotting points
- geom_bar() - for plotting bar graph
- geom_line() - for plotting line chart
- geom_violin() - for plotting violin plot
The basic syntax of gggplot2 plots is:
ggplot(data, mapping = aes(x =, y=)) + geometric object
where:
- data : Dataframe that is used to plot the chart
- mapping = aes() : aesthetic mapping which deals with controlling axis (x and y indicates the different variables)
- geometric object : Indicates the code for typeof plot you need to visualise.
This recipe demonstrates how to make a violin plot using ggplot2.
STEP 1: Loading required library and dataset
Dataset description: It is the basic data about the customers going to the supermarket mall. The variable that we interested in is Annual.Income which is in 1000s.
# Data manipulation package
library(tidyverse)
# ggplot for data visualisation
library(ggplot2)
# reading a dataset
customer_seg = read.csv('Mall_Customers.csv')
glimpse(customer_seg)
Rows: 200 Columns: 5 $ CustomerID1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 1... $ Gender Male, Male, Female, Female, Female, Female, ... $ Age 19, 21, 20, 23, 31, 22, 35, 23, 64, 30, 67, ... $ Annual.Income..k.. 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 19, ... $ Spending.Score..1.100. 39, 81, 6, 77, 40, 76, 6, 94, 3, 72, 14, 99,...
STEP 2: Plotting a violin plot using ggplot
We use geometric object as geom_violin() to plot a violin plot of Annual Income variable based on the gender
Note:
- The + sign in the syntax earlier makes the code more readable and enables R to read further code without breaking it.
- fill arguement inside the geom_violin() o fill the violinplot based on a factor
- We also use labs() function to give a title to the graph
ggplot(customer_seg, aes(x = Gender, y = Annual.Income..k..)) + geom_violin(aes(fill = Gender)) + labs(title = "Annual Income Violin Plot")
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