Legends - R Graphics - page 305

Changing the Labels in a Legend
Problem
You want to change the text of labels in a legend.
Solution
Set the labels in the scale ( Figure 10-13 , left):
library(gcookbook) # For the data set
# The base plot
p <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) + geom_boxplot()
# Change the legend labels
p + scale_fill_discrete(labels = c( "Control" , "Treatment 1" , "Treatment 2" ))
Figure 10-13. Left: manually specified legend labels with the default discrete scale; right: manu-
ally specified labels with a different scale
Discussion
Note that the labels on the x-axis did not change. To do that, you would have to set the labels
of scale_x_discrete() ( Changing the Text of Axis Labels ) , or change the data to have differ-
ent factor level names ( Changing the Names of Factor Levels ) .
In the preceding example, group was mapped to the fill aesthetic. By default this uses
scale_fill_discrete() , which maps the factor levels to colors that are equally spaced around
the color wheel (the same as scale_fill_hue() ). There are other fill scales we could use,