[R-sig-Geo] How do I calculate neighborhood contiguity in R?

[Shanley Thompson]

Hello,
My end goal is to calculate join counts, using the function
joincounts.multi() from the R package spdep. I understand that first I need
to calculate the nb object, then the spatial weights matrix, then I can do
the join counts. 

I have a very large raster file (nrows = 19663, ncols = 34073), with cell
size of 30 m, in integer format. I read it in using the raster() function
from the Raster package.

For the first part (creating a "nb" object), I have tried using the cell2nb
file but it keeps crashing - a quick search tells me others have had the
same problem due to large files.  

I read that one can use "dnearneigh" function in the spdep package instead,
but I do not understand how to do so. Can someone provide a detailed
example?  Alternatively, would it be better to convert my raster layer to a
polygon layer then use the function poly2nb? 

I am relatively new to R so the simpler the better!

Thank you so much! 


Shanley Thompson, MSc, PhD Candidate
Department of Geography, University of Victoria, Canada