triu - Upper triangular part of matrix - MATLAB (original) (raw)

Main Content

Upper triangular part of matrix

Syntax

Description

U = triu([A](#d126e1919572),[k](#d126e1919624)) returns the elements on and above the kth diagonal of A.

Examples

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Create a 4-by-4 matrix of ones. Extract the upper triangular portion.

A = 4×4

 1     1     1     1
 1     1     1     1
 1     1     1     1
 1     1     1     1

B = 4×4

 1     1     1     1
 0     1     1     1
 0     0     1     1
 0     0     0     1

Extract only the elements above the main diagonal.

C = 4×4

 0     1     1     1
 0     0     1     1
 0     0     0     1
 0     0     0     0

Input Arguments

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Input matrix.

Diagonals to include, specified as a scalar. k = 0 is the main diagonal, k > 0 is above the main diagonal, and k < 0 is below the main diagonal.

Matrix with the main diagonal labeled as k=0. Values of k greater than zero are for diagonals above the main diagonal, and values of k less than zero are for diagonals below the main diagonal.

Example: triu(A,3)

More About

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The upper triangular portion of a matrix includes the main diagonal and all elements above it. The shaded elements in this graphic depict the upper triangular portion of a 6-by-6 matrix.

6-by-6 matrix with shaded elements on and above the main diagonal.

Extended Capabilities

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Usage notes and limitations:

If you supply the argument that represents the order of the diagonal matrix, then it must be a real and scalar integer value.

Usage notes and limitations:

If you supply the argument that represents the order of the diagonal matrix, then it must be a real and scalar integer value.

The triu function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a