[R-sig-Geo] Neighbours list

[Ronnie Babigumira]

Hi, I have a raster map in raster format and would like to make a neighbours list. Reading spdeps documentation I sense 
that cell2nb is what I should use, however, my grid is not regular (my understanding of this that the grid would be a 
square or rectangle yet my grid is an abstract form of a region in a country). How does one go about creating a 
neighbours list in such a case?

Ronnie