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# triu

Upper triangular part of matrix

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

## Description

example

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

U = triu(A,k) 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 = 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.

Example: triu(A,3)

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### Upper Triangular

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