Pie charts are used to display the distribution of a single categorical variable.

All of the plots below use tools from the ggplot2 and dplyr packages.

library(ggplot2)  # Loads the ggplot2 library
library(dplyr)  # Loads the dplyr library

Pie Chart

Below is the code used to create a pie chart of the class variable from the mpg dataset that is part of the ggplot2 package. .

mpg %>% 
  ggplot(aes(x = "", fill = class)) + 
  geom_bar(position = "fill", width = 1) + 
  coord_polar(theta = "y") + 
  labs( 
    title = "Automobile Class",
    x = "", 
    y = ""
  )

The extranious numbers and lines around the pie chart can be removed using the theme() arguement.

mpg %>% 
  ggplot(aes(x = "", fill = class)) + 
  geom_bar(position = "fill", width = 1) + 
  coord_polar(theta = "y") + 
  labs( 
    title = "Automobile Class", 
    x = "", 
    y = ""
  ) + 
  theme(
    panel.grid = element_blank(), 
    axis.ticks = element_blank(), 
    axis.text.x=element_blank(), 
    panel.border = element_blank())

Multiple Pie Charts

Below is the code used to create side-by-side pie charts of automobile class separated by drive train using the mpg dataset that is part of the ggplot2 package.

mpg %>% 
  ggplot(aes(x = "", fill = class)) + 
  geom_bar(position = "fill", width = 1) + 
  coord_polar(theta = "y") + 
  labs( 
    title = "Automobile Class by Drive Train",
    x = "", 
    y = ""
  ) + 
  theme(
    panel.grid = element_blank(), 
    axis.ticks = element_blank(), 
    axis.text.x=element_blank(), 
    panel.border = element_blank() 
    ) + 
  facet_grid(. ~ drv)

Mathematicss, Computer Science, and Statistics Department Gustavus Adolphus College