[R] shade between two curves

[David Bickel]

Is there a function that can shade the region between two arbitrary
curves? For example, how can I fill in the area between these two
plotted lines?

> x <- 1:10
> y <- x + rnorm(10)
> z <- x + 10 + rnorm(10)
> plot(x, y, type = "l", ylim = c(0,20))
> lines(x, z)

I would appreciate any help.

David