Band

Band[{i, j}] represents the sequence of positions on the diagonal band that starts with {i, j} in a sparse array.

Band[{imin, jmin, ...}, {imax, jmax, ...}] represents the positions between {imin, jmin, ...} and {imax, jmax, ...}.

Band[{imin, jmin, ...}, {imax, jmax, ...}, {di, dj, ...}] represents positions starting with {imin, jmin, ...} and then moving with step {di, dj, ...}.

Examples

Create a diagonal matrix:

SparseArray[Band[{1, 1}] -> {a, b, c}]
(* diagonal matrix with a, b, c on the diagonal *)

Please visit the official Wolfram Language Reference for more details.