description: B = triu(A,k) extracts upper triangular part of A. triu(A) is the upper triangular part of A. triu(A,k) is the elements on and above the k-th diagonal of A. k = 0 is the main diagonal, k > 0 is above the main diagonal and k < 0 is below the main diagonal. arguments: A is a matrix of NCpolys k is an integer output: matrix of NCpolys possible usage: triu(A), triu(A,k) example: >> A=[x x^2 x*y-y*x; y x*y 2*x-y; x+y y-x x^2+y^2]
A = x x^2 x*y-y*x y x*y 2*x-y x+y -x+y x^2+y^2 >> triu(A) ans = x x^2 x*y-y*x 0 x*y 2*x-y 0 0 x^2+y^2 >> triu(A,-1) ans = x x^2 x*y-y*x y x*y 2*x-y 0 -x+y x^2+y^2 |