UpperTriangularMatrix

UpperTriangularMatrix[umat] converts the upper triangular matrix umat to a structured array.

Examples

UpperTriangularMatrix[{{1, 2, 3}, {0, 4, 5}, {0, 0, 6}}]

Normal[UpperTriangularMatrix[{{1, 2}, {0, 3}}]]

Please visit the official Wolfram Language Reference for more details.