[R-sig-Geo] Map of pixel area?

[Jonathan Greenberg]

R-sig-geo'ers:

I have an analysis where I need to take a geographic projection map, e.g.:

r1 <- raster()

And calculate, for each pixel, the square kilometers that each individual
pixel covers (since they vary across a geographic projection) -- the idea
is to end up with a map of pixel area.  Can anyone think of a clever way to
do this?  I'll be using this to do some area weighted summaries, but I
can't simply reproject the input map.  Thanks!

--j

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