TRIL

Purpose:

Returns the lower triangle of a matrix.

TRIL(a, d)

a	-	A matrix.
d	-	Optional. An integer, the diagonal on and below which to include matrix elements. Defaults to 0, the main diagonal.

An array consisting of the lower triangle of a where the other elements are zero.

W1: {{1, 2, 3},

{4, 5, 6},

{7, 8, 9}}

W2: tril(W1)

W2 == {{1, 0, 0},

{4, 5, 0},

{7, 8, 9}}

W3: tril(W1, 1)

W3 == {{1, 2, 0},

{4, 5, 6},

{7, 8, 9}}

W4: tril(W1, -1)

W4 == {{0, 0, 0},

{4, 0, 0},

{7, 8, 0}}

TRIL(a, -1) is equivalent to LOTRIX(a).

See TRIU to return the upper matrix.