Home » How to Change the Legend Title in ggplot2 (With Examples)

How to Change the Legend Title in ggplot2 (With Examples)

by Tutor Aspire

There are two easy ways to change the legend title in a ggplot2 chart:

Method 1: Use labs()

ggplot(data, aes(x=x_var, y=y_var, fill=fill_var)) + 
  geom_boxplot() + 
  labs(fill='Legend Title')

Method 2: Use scale_fill_manual()

ggplot(data, aes(x=x_var, y=y_var, fill=fill_var)) + 
  geom_boxplot() +
  scale_fill_manual('Legend Title', values=c('color1', 'color2'))

This tutorial shows examples of how to use these two methods in practice.

Method 1: Change Legend Title Using labs()

The following code shows how to create a grouped boxplot for a given dataset:

library(ggplot2) 

#create dataset
data rep(c('A', 'B', 'C'), each=50),
                   program=rep(c('low', 'high'), each=25),
                   values=seq(1:150)+sample(1:100, 150, replace=TRUE))

#create boxplot
ggplot(data, aes(x=team, y=values, fill=program)) + 
  geom_boxplot()

By default, ggplot2 uses the variable name in the dataset as the legend title. However, we can use the labs() function to easily change it:

library(ggplot2) 

#create dataset
data rep(c('A', 'B', 'C'), each=50),
                   program=rep(c('low', 'high'), each=25),
                   values=seq(1:150)+sample(1:100, 150, replace=TRUE))

#create boxplot
ggplot(data, aes(x=team, y=values, fill=program)) + 
  geom_boxplot() + 
  labs(fill='Program Type')

Change legend title in ggplot2

We can also add a line break in the legend title by placing n wherever we’d like the new line to start:

library(ggplot2) 

#create dataset
data rep(c('A', 'B', 'C'), each=50),
                   program=rep(c('low', 'high'), each=25),
                   values=seq(1:150)+sample(1:100, 150, replace=TRUE))

#create boxplot
ggplot(data, aes(x=team, y=values, fill=program)) + 
  geom_boxplot() + 
  labs(fill='ProgramnType')

Change legend title and add line break in ggplot2

Method 2: Change Legend Title Using scale_fill_manual()

We can also use the scale_fill_manual() function to simultaneously specify a legend title and a vector of color values to use:

library(ggplot2) 

#create dataset
data rep(c('A', 'B', 'C'), each=50),
                   program=rep(c('low', 'high'), each=25),
                   values=seq(1:150)+sample(1:100, 150, replace=TRUE))

#create boxplot
ggplot(data, aes(x=team, y=values, fill=program)) + 
  geom_boxplot() + 
  scale_fill_manual('Program Type', values=c('pink','blue'))

Change legend title in ggplot2 using scale_fill_manual

Note that the values for the colors can either be names or hex color codes.

Additional Resources

A Complete Guide to the Best ggplot2 Themes
The Complete Guide to ggplot2 Titles
How to Create Side-by-Side Plots in ggplot2

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