Adding Points to filled.contour in R - at the right place

Question

I'd like to add a point to an existing filled.contour plot, using the following code:

MyFunction <- function(x,y){
   return(dnorm(sqrt(x^2+y^2)))
}
wrapper <- function(x, y, my.fun, ...) {sapply(seq_along(x), FUN = function(i) my.fun(x[i], y[i], ...))}
meshstep <- 0.5
x<- seq(-20,20,meshstep)
y <-seq(-20,20,meshstep)
z <- outer(x,y,FUN = wrapper, my.fun=MyFunction)
filled.contour(x,y,z, col=rev(heat.colors(n=20, alpha=0.7)), nlevels=15)
points(0,0)

I'm pretty surprised that points(0,0) didn't put a point into the origin of the plot, but roughly located at x=10,y=0. Also, locator() seems to be prompting coordinates with respect to that 'new' coordinate system as well. Why is that?

Answer 1

You can find a detailed answer here : Plotting a box within filled.contour plots in R?

In short, filled.contour use two different coordinates system, one for the filled contour and one for the legend. To solve your problem, you either have to use another function, or to put your points into the plot.axes argument :

filled.contour(x,y,z, col=rev(heat.colors(n=20, alpha=0.7)), nlevels=15,
               plot.axes={points(0,0)})