TRIU

Purpose:

Returns the upper triangle of a matrix.

TRIU(a, d)

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

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

W1: {{1, 2, 3},

{4, 5, 6},

{7, 8, 9}}

W2: triu(W1)

W2 == {{1, 2, 3},

{0, 5, 6},

{0, 0, 9}}

W3: triu(W1, 1)

W3 == {{0, 2, 3},

{0, 0, 6},

{0, 0, 0}}

W4: triu(W1, -1)

W4 == {{1, 2, 3},

{4, 5, 6},

{0, 8, 9}}

TRIU(a, 1) is equivalent to UPTRIX(a).

See TRIL to return the lower matrix.