# triu

Upper triangular part of matrix

## Syntax

``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 elements in this graphic depict the upper triangular portion of a 6-by-6 matrix. ## Version History

Introduced before R2006a