Gradient in geom_ribbon

Question

I have the following ggplot2 code that displays a tape from 3rd to 97th quartile:

 h <- ggplot(l, aes(x=age[limit])) h <- h + geom_ribbon(aes(ymin=X3rd[limit], ymax=X97th[limit]), fill="gray80") h 

The geom_ribbon man page shows that gradient, gradient2, etc. are “linked scales” to fill for this geometry. I need the tape to be light gray on the outside, to a dark gray in the middle, then again light gray on the outside, but I get the impression (and some results on Google reinforce this impression) that the gradients cannot actually be applied to the tape.

Answer 1

geom_ribbon does not support gradient. Instead, if I understand correctly what you want to do, overlapping tapes can be useful:

 d <- data.frame(x=1:10, m=runif(10)) d <- transform(d, l1=m-1, l2=m-2, u1=m+1, u2=m+2) ggplot(d, aes(x)) + geom_ribbon(aes(ymin=l2, ymax=u2), fill="grey60") + geom_ribbon(aes(ymin=l1, ymax=u1), fill="grey40")