Draw A Map of China onto A Color Image

What we need to do is just use the parameter add = TRUE in the function of map() (package maps):

Source code:

if (require(maps) && require(mapdata)) {
  par(mar = c(0, 0, 0, 0))
  map("china")
  bd = par()$usr  #get the border
  x = seq(bd[1], bd[2], length = 100)
  y = seq(bd[3], bd[4], length = 100)
  z = sqrt(outer((x - mean(x))^2, (y - mean(y))^2, "+"))
  image(x, y, z, col = cm.colors(25), axes = F, xlab = "", ylab = "")
  map("china", add = TRUE) # add the map to the color image
}

Packages maps and mapdata are required for the map of China.