[R-sig-Geo] Coarsening grid, but producing max, min, and mean layers

[Nick Matzke]

Hi all,

I've got a georeferenced grid with elevation data (height of 
land, depth below sea level).  I have loaded it into R in 
various formats.

I would like to coarsen it to match other environmental 
datasets for species distribution modeling purposes, but I 
feel that the coarsened grid should include some of the 
information from the finer-resolution layer -- e.g., if a 
coarse grid cell has an island in it, the depth should not 
simply be the mean of the finer pixels, there should be a 
layer than says "min depth=0" for that pixel.

So, I would like to have 3 coarse layers, with max(depth), 
min(depth), and mean(depth).

What would be the most efficient method/R function for 
coarsening a grid in this fashion?

Help much appreciated!!

Cheers!
Nick


-- 
====================================================
Nicholas J. Matzke
Ph.D. Candidate, Graduate Student Researcher

Huelsenbeck Lab
Center for Theoretical Evolutionary Genomics
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Department of Integrative Biology
University of California, Berkeley

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