[R-sig-Geo] Efficient way to obtain gridded count of overlapping polygons?

[Robert Hijmans]

> I am interested in creating a raster that summarizes the number of 
> overlapping polygons that underlie each cell (in order to display how 
> many species occur at that point). 

Lyndon, 

You can also do the below, with raster, see ?rasterize:

r <- rasterize(pols, r, fun='count')

or 

r <- rasterize(pols, r, fun=function(x,...)length(na.omit(x)))


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