13.16 Creating a Pie Chart

13.16.1 Problem

You want to make a pie chart.

13.16.2 Solution

Use the pie() function. In this example (Figure 13.31), we’ll use the survey data set from the MASS library:

library(MASS) # For the data set
# Get a table of how many cases are in each level of fold
fold <- table(survey$Fold)
fold
#> 
#>  L on R Neither  R on L 
#>      99      18     120

# Reduce margins so there's less blank space around the plot
par(mar = c(1, 1, 1, 1))
# Make the pie chart
pie(fold)

Figure 13.31: A pie chart

We passed pie() an object of class table. We could have instead given it a named vector, or a vector of values and a vector of labels like this, with the same result:

pie(c(99, 18, 120), labels = c("L on R", "Neither", "R on L"))

13.16.3 Discussion

The lowly pie chart is the subject of frequent abuse from data visualization experts. If you’re thinking of using a pie chart, consider whether a bar graph (or stacked bar graph) would convey the information more effectively. Despite their faults, pie charts do have one important virtue: everyone knows how to read them.