I am trying to visualize heavily tailed raster data, and I would like a non-linear mapping of colors to the range of the values. There are a couple of similar questions, but the
This code will make manual breaks with a pnorm transformation. Is this what you are after?
ggplot(dat, aes(x = x, y = y, fill = z)) + geom_tile(width=2, height=30) + scale_fill_gradientn(colours=fill.colors, trans = 'norm', breaks = quantile(dat$z, probs = c(0, 0.25, 1)) )