Question

Seemingly a very simple thing to do but it took me >30min without finding answer.

How do I reverse the order of colors? By looking at documentation for scale_brewer, i figured it can be formatter= argument being suspicious. I passed 'rev' and then rev, but they have no effect (no error message, just ignored).

Answer 1

I think you probably want to select the colors using brewer.pal directly and then use scale_colour_manual:

library(ggplot2)
library(RColorBrewer)

ggplot(mtcars,aes(x = mpg, y = disp)) + 
    geom_point(aes(colour = factor(cyl))) + 
    scale_colour_manual(values = rev(brewer.pal(3, "BuPu")))

Then you can rev the order of the colors there.

As of version 2.0,0 of ggplot there is now a more direct way to do this, see the answer by @pbaylis below.