Converts a nearest neighbor index matrix into a sparse adjacency matrix. The resulting matrix
is non-symmetric (i can be neighbor of j without j being neighbor of i). Note that the matrix
orientation places neighbors in rows and source cells in columns.
Arguments
- .nn.idx
A matrix where each row represents a cell and each column represents a nearest
neighbor index. Element (i,k) is the index of the k-th nearest neighbor of cell i.
Value
A non-symmetric sparse matrix (dgCMatrix) of dimensions n×n where n is the number of
cells. Entry (j,i) = 1 if j is among i's nearest neighbors, 0 otherwise. That is, row j
contains 1s in columns corresponding to cells that have j as a neighbor.
