ggplot2 - shade area between two vertical lines [duplicate]

Answer 1

It might be even easier to use annotate() for this if you know the coordinates for which region you want to shade. I had some strange rendering problems when I tried to use geom_rect().

library(ggplot2)
data(mtcars)

ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point() +
     annotate("rect", xmin = 3, xmax = 4.2, ymin = 12, ymax = 21,
        alpha = .2)

I know it's essentially the same thing; I just happened stumbled on this tidbit from here.