Symbolic Math Toolbox

triu

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

tril

vpa