Legends - R Graphics - page 294

Figure 10-4. Left: legend with opaque background and outline; right: with no background or out-
lines

You can also remove the border around its elements so that it blends in ( Figure 10-4 , right):

p + theme(legend.position = c( .85 , .2 )) +
theme(legend.background = element_blank()) + # Remove overall border
theme(legend.key = element_blank()) # Remove border around each item

Changing the Order of Items in a Legend

Problem
You want to change the order of the items in a legend.

Solution
Set the limits in the scale to the desired order ( Figure 10-5 ):

# The base plot
p <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) + geom_boxplot()
p

# Change the order of items
p + scale_fill_discrete(limits = c( "trt1" , "trt2" , "ctrl" ))