In modeling spatial association, a key issue is the neighbor's definition
which captures the spatial proximity matrix W. For a set of N spatial
entities, it is usual to define the contiguity relation in terms of sets N(i)
of neighbors of spatial entity or site i. These are coded in the form of a
weights matrix W⁎, with a zero diagonal, and the off-diagonal non
zero elements often scaled to sum to unity in each row (standardized
weights matrices), with typical elements: