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.
Donate
As a freelancer (currently working as a contractor) and a dad of three kids, I truly appreciate your donation to support my writing and open-source software development! Your contribution helps me cope with financial uncertainty better, so I can spend more time on producing high-quality content and software. You can make a donation through methods below.
When sending money, please be sure to add a note “gift” or “donation” if possible, so it won’t be treated as my taxable income but a genuine gift. Needless to say, donation is completely voluntary and I appreciate any amount you can give.
Please feel free to email me if you prefer a different way to give. Thank you very much!
I’ll give back a significant portion of the donations to the open-source community and charities. For the record, I received about $30,000 in total (before tax) in 2024-25, and gave back about $15,000 (after tax).
