is_triu

is_triu(matrix: any[] | Mat) : boolean

param matrix - Any matrix, 2 dimensional and square, to test if it's an upper triangular matrix or not

returns: boolean - true if it is upper triangular, false otherwise.

This function tests if a square 2-D matrix is upper triangular or not. Upper triangular matrices have the property that everything below the diagonal is zero, hence only the upper diagonal (shaped like a triangle) has values. For a visual method, look at the diagonal and see if there's any entry below the diagonal that is non zero. If there is, it is not upper triangular.