# relu

Apply rectified linear unit activation

## Syntax

``Y = relu(X)``

## Description

The rectified linear unit (ReLU) activation operation performs a nonlinear threshold operation, where any input value less than zero is set to zero.

This operation is equivalent to

`$f\left(x\right)=\left\{\begin{array}{cc}x,& x>0\\ 0,& x\le 0.\end{array}$`

Note

This function applies the ReLU operation to `dlarray` data. If you want to apply ReLU activation within a `layerGraph` object or `Layer` array, use the following layer:

example

````Y = relu(X)` computes the ReLU activation of the input `X` by applying a threshold operation. All values in `X` that are less than zero are set to zero.```

## Examples

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Use the `relu` function to set negative values in the input data to zero.

Create the input data as a single observation of random values with a height and width of 12 and 32 channels.

```height = 12; width = 12; channels = 32; observations = 1; X = randn(height,width,channels,observations); X = dlarray(X,'SSCB');```

Compute the leaky ReLU activation.

`Y = relu(X);`

All negative values in `X` are now set to `0`.

## Input Arguments

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Input data, specified as a formatted `dlarray`, an unformatted `dlarray`, or a numeric array.

Data Types: `single` | `double`

## Output Arguments

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ReLU activations, returned as a `dlarray`. The output `Y` has the same underlying data type as the input `X`.

If the input data `X` is a formatted `dlarray`, `Y` has the same dimension format as `X`. If the input data is not a formatted `dlarray`, `Y` is an unformatted `dlarray` with the same dimension order as the input data.

## Version History

Introduced in R2019b