Slope and Aspect calculations in R

Hello

We are looking to mimic, in R, the slope (max magnitude difference 
between a cell and its neighbors) and aspect (direction of maximum 
magnitude difference) functions found in ESRI's Spatial Analyst package. 
We were just about to code up the slope function but thought I would 
make sure we weren't re-inventing any wheels already out there.

Thanks
Josh

Josh M. London, PhD

Wildlife Biologist
Polar Ecosystem Program
National Marine Mammal Lab
Alaska Fisheries Science Center, NOAA Fisheries
Seattle, WA

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