3-d plots with R{ggplot2}: The “Volcano Plot”

From the stat_contour {ggplot2} help

library(ggplot2)
library(reshape2)
volcano3d <- melt(volcano)
names(volcano3d) <- c("x", "y", "z")
v <- ggplot(volcano3d, aes(x, y, z = z))
v + stat_contour(geom="polygon", aes(fill=..level..))