Symbolic upper triangle.
Syntax
triu(X)
triu(X, K)
Description
triu(X) is the upper triangular part of X.
triu(X, K) returns an upper triangular matrix that retains the elements of X on and above the k-th diagonal and sets the remaining elements to 0. The values k=0, k>0, and k<0 correspond to the main, superdiagonals, and subdiagonals, respectively.
Examples
Suppose
A =
[ a, b, c ]
[ 1, 2, 3 ]
[ a+1, b+2, c+3 ]
Then triu(A) returns
[ a, b, c ]
[ 0, 2, 3 ]
[ 0, 0, c+3 ]
triu(A,1) returns
[ 0, b, c ]
[ 0, 0, 3 ]
[ 0, 0, 0 ]
triu(A,-1) returns
[ a, b, c ]
[ 1, 2, 3 ]
[ 0, b+2, c+3 ]
See Also
diag, tril
[ Previous | Help Desk | Next ]