[R] Smoothing z-values according to their x, y positions

[Emmanuel Levy]

Dear All,

I'm sure this is not the first time this question comes up but I
couldn't find the keywords that would point me out to it - so
apologies if this is a re-post.

Basically I've got thousands of points, each depending on three variables:
x, y, and z.

if I do a plot(x,y, col=z), I get something very messy.

So I would like to smooth the values of z according to the values of
their neighbors (given by x and y).

Could you please point me out to the function(s) I should look into
for the smothing, and
possibly for the plotting?

Many thanks for your help,

Emmanuel