ggplot2 reverse order of scale_brewer

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

The CRAN version of ggplot2 now allows users to specify direction=-1 in scale_brewer to reverse the colors. The following produces the same plot as the accepted answer.

ggplot(mtcars,aes(x = mpg, y = disp)) + 
  geom_point(aes(colour = factor(cyl))) + 
  scale_colour_brewer(palette="BuPu", direction=-1)

Answer 2

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.

Answer 3

This will not help with the OP's problem - I know. For discrete scales like scale_..._brewer(), doing scale_..._manual(values = rev(colorsYouHad)) is the right answer.

Nevertheless, for continuous scales, you can simply pass:

scale_..._...(..., trans = "reverse")

e.g., for the continuous equivalent of scale_..._brewer():

scale_..._distiller("My Scale", palette = "Spectral", trans = "reverse")

Answer 4

If you don't want to muck around directly with RColorBrewer (a lovely package), you can reverse the levels of the factor in the original data.frame, and then plot it:

dsamp <- diamonds[sample(nrow(diamonds), 1000), ] 

# Reverse the levels of the factor associated with color, here 'clarity'
# (Might be safer to assign this to a new column named, e.g., 'clarity2')
levels(dsamp$clarity) <- rev(levels(dsamp$clarity))

d <- qplot(carat, price, data = dsamp, colour = clarity)
d + scale_colour_brewer(breaks = levels(dsamp$clarity))

And if you want to print the key in the same order as before the reversal, just do this:

d + scale_colour_brewer(breaks = rev(levels(dsamp$clarity)))