create neighbourhood (nb) object from grid geometry
gridIndex2nb(obj, maxdist = sqrt(2), fullMat = TRUE, ...)object of class SpatialGrid or SpatialPixels
maximum distance to be considered (inclusive), expressed in number of grid cell (sqrt(2) results in queen neighbours)
use dist to compute distances from grid (row/col) indices; FALSE avoids forming the full distance matrix, at a large performance cost
arguments passed on to dist
Object of class nb, which is a list.
The nb object follows the convention of nb objects in package spdep; it is a list with each list element corresponding to a grid cell or pixel; the list element contains the indices of neighbours defined as cells less than maxdist away, measured in cell unit (N/S/E/W neighbour has distance 1).
plot.nb in package spdep