A pie chart is a type of chart that is shaped like a circle and uses slices to represent proportions of a whole.

This tutorial explains how to create and modify pie charts in R using the ggplot2 data visualization library.

How to Make a Basic Pie Chart

The following code shows how to create a basic pie chart for a dataset using ggplot2:

library(ggplot2)

#create data frame
data <- data.frame("category" = c('A', 'B', 'C', 'D'),
                   "amount" = c(25, 40, 27, 8))

#create pie chart
ggplot(data, aes(x="", y=amount, fill=category)) +
  geom_bar(stat="identity", width=1) +
  coord_polar("y", start=0) 

How to Modify the Appearance of the Pie Chart

The default pie chart in ggplot2 is quite ugly. The simplest way to improve the appearance is to use theme_void(), which removes the background, the grid, and the labels:

ggplot(data, aes(x="", y=amount, fill=category)) +
  geom_bar(stat="identity", width=1) +
  coord_polar("y", start=0) +
  theme_void()

We can further improve the appearance of the chart by adding labels inside the slices:

ggplot(data, aes(x="", y=amount, fill=category)) +
  geom_bar(stat="identity", width=1) +
  coord_polar("y", start=0) +
  geom_text(aes(label = paste0(amount, "%")), position = position_stack(vjust=0.5)) +
  labs(x = NULL, y = NULL, fill = NULL)

We can customize the chart even further by specifying our own hex colors to use for the slices with the scale_fill_manual() argument:

ggplot(data, aes(x="", y=amount, fill=category)) +
  geom_bar(stat="identity", width=1) +
  coord_polar("y", start=0) +
  geom_text(aes(label = paste0(amount, "%")), position = position_stack(vjust=0.5)) +
  labs(x = NULL, y = NULL, fill = NULL) +
  theme_classic() +
  theme(axis.line = element_blank(),
          axis.text = element_blank(),
          axis.ticks = element_blank()) +
  scale_fill_manual(values=c("#FF5733", "#75FF33", "#33DBFF", "#BD33FF"))

Tip: Use this Hex Color Picker to find combinations of hex color codes that go well together.

ggplot(data, aes(x="", y=amount, fill=category)) +
  geom_bar(stat="identity", width=1) +
  coord_polar("y", start=0) +
  geom_text(aes(label = paste0(amount, "%")), position = position_stack(vjust=0.5)) +
  labs(x = NULL, y = NULL) +
  theme_classic() +
  theme(axis.line = element_blank(),
          axis.text = element_blank(),
          axis.ticks = element_blank()) +
  scale_fill_brewer(palette="Blues")

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