triu (Symbolic Math Toolbox)

triu	Examples See Also

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 ]