Question

Having a hard time with labels on a ggplot2 plot. Here’s a similar plot from the examples page:

mt <- ggplot(mtcars, aes(mpg, wt, colour = factor(cyl))) + geom_point() 
mt + facet_grid(. ~ cyl, scales = "free")

How would I define a list of labels for factor(cyl)?

Answer 1

You can define it in the labels argument to the colour scale:

ggplot(mtcars, aes(mpg, wt, colour=factor(cyl))) + 
  geom_point() +
  scale_colour_discrete(breaks = c("4", "6", "8"),
                        labels = c("Four", "Six", "Eight"))