asymmetric color distribution in scale_gradient2?

Question

Changing the upper limits for scale_fill_gradient2 also effects the colorscaling for values < 0 as the color distribution around 0 seems to be always symmetr

Answer 1

What you want is scale_fill_gradientn. The arguments are not very clear (took me an hour or so to finally figure part of it out), though:

library("scales")
p + scale_fill_gradientn(colours = c("blue","white","red"), 
                         values = rescale(c(-.1,0,.3)),
                         guide = "colorbar", limits=c(-.1,.3))

Which gives: