[R-sig-Geo] Map layer

[Fernando Miguez]

Hi all,

I would like to be able to do the following

map('state','illinois')
points(x,y)

Up to this point everything is fine. However, some of the points fall 
outside the Illinois map boundaries. What I would like to do is to add a 
layer where the inside of the Illinois polygon is transparent (so that 
the points can be seen) but the points outside the boundary are covered 
so they are not seen. I thought that using some variation of map with 
its arguments would work, but I haven't been able to figure it out. I 
see that it is quite possible that I'm using the wrong tools all 
together ... let me know.

Any help is appreciated. Thanks.

Fernando

-- 
Fernando E. Miguez
Energy Biosciences Institute
https://netfiles.uiuc.edu/miguez/www