Simple pie charts

Create some data :

df <- data.frame(
  group = c("Male", "Female", "Child"),
  value = c(25, 25, 50)
  )
head(df)

##    group value
## 1   Male    25
## 2 Female    25
## 3  Child    50

Use a barplot to visualize the data :

library(ggplot2)
# Barplot
bp<- ggplot(df, aes(x="", y=value, fill=group))+
geom_bar(width = 1, stat = "identity")
bp

Create a pie chart :

pie <- bp + coord_polar("y", start=0)
pie

Change the pie chart fill colors

It is possible to change manually the pie chart fill colors using the functions :

• scale_fill_manual() : to use custom colors
• scale_fill_brewer() : to use color palettes from RColorBrewer package
• scale_fill_grey() : to use grey color palettes

# Use custom color palettes
pie + scale_fill_manual(values=c("#999999", "#E69F00", "#56B4E9"))

# use brewer color palettes
pie + scale_fill_brewer(palette="Dark2")

pie + scale_fill_brewer(palette="Blues")+
  theme_minimal()

# Use grey scale
pie + scale_fill_grey() + theme_minimal()

Read more on ggplot2 colors here : ggplot2 colors

Create a pie chart from a factor variable

PlantGrowth data is used :

head(PlantGrowth)

##   weight group
## 1   4.17  ctrl
## 2   5.58  ctrl
## 3   5.18  ctrl
## 4   6.11  ctrl
## 5   4.50  ctrl
## 6   4.61  ctrl

Create the pie chart of the count of observations in each group :

ggplot(PlantGrowth, aes(x=factor(1), fill=group))+
  geom_bar(width = 1)+
  coord_polar("y")

Customized pie charts

Create a blank theme :

blank_theme <- theme_minimal()+
  theme(
  axis.title.x = element_blank(),
  axis.title.y = element_blank(),
  panel.border = element_blank(),
  panel.grid=element_blank(),
  axis.ticks = element_blank(),
  plot.title=element_text(size=14, face="bold")
  )

1. Apply the blank theme
2. Remove axis tick mark labels
3. Add text annotations : The package scales is used to format the labels in percent

# Apply blank theme
library(scales)
pie + scale_fill_grey() +  blank_theme +
  theme(axis.text.x=element_blank()) +
  geom_text(aes(y = value/3 + c(0, cumsum(value)[-length(value)]), 
            label = percent(value/100)), size=5)

# Use brewer palette
pie + scale_fill_brewer("Blues") + blank_theme +
  theme(axis.text.x=element_blank())+
  geom_text(aes(y = value/3 + c(0, cumsum(value)[-length(value)]), 
                label = percent(value/100)), size=5)

Infos

This analysis has been performed using R software (ver. 3.1.2) and ggplot2 (ver. 1.0.0)

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