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triu

Upper triangular part of matrix

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Syntax

U = triu(A)
U = triu(A,k)

Description

U = triu(A) returns the upper triangular portion of matrix A.

example

U = triu(A,k) returns the elements on and above the kth diagonal of A.

Examples

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Open Live Script

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

A = ones(4)
A = 4×4

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


B = triu(A)
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 = triu(A,1)
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.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char
Complex Number Support: Yes

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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Upper Triangular

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

Version History

Introduced before R2006a

See Also

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