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# PHP | stats_rand_gen_exponential() Function

Hello folks! welcome back to a new edition of our tutorial on PHP. In this tutorial guide, we are going to be studying about the PHP stats_rand_gen_exponential() Function.

The stats_rand_gen_exponential() function is used to generate a random deviate from the exponential distribution.

## Syntax

Following below is the syntax to use this function -

`float stats_rand_gen_exponential( float \$av )`

## Parameter Details

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1

av

The scale parameter

## Return Value

This PHP function returns a random deviate from the exponential distribution, where the scale parameter is av.

## Dependencies

This built-in function was first introduced in statistics extension (PHP version 4.0.0 and PEAR v1.4.0). In this tutorial guide, we used the latest release of stats-2.0.3 (PHP v7.0.0 or newer and PEAR version 1.4.0 or newer).

### Example1

Following example computes the random deviation from the exponential distribution -

```<?php
var_dump(is_float(stats_rand_gen_exponential(2)));
?>```

#### Output

When the above code is executed, it will produce the following result -

`bool(true)`

### Example2

In below example, we compute the random deviation from the exponential distribution by passing 0 as scale parameter -

```<?php
var_dump(stats_rand_gen_exponential(0));
?>```

#### Output

When the above code is executed, it will produce the following result -

`float(0)`

### Example3

The following below is an error case. In the following example, we have passed av < 0. A warning is shown in logs -

```<?php
// error cases
var_dump(stats_rand_gen_exponential(-0.1)); // av < 0
?>```

#### Output

The above code will produce the following result and a warning in logs PHP Warning: stats_rand_gen_exponential(): av < 0.0

`bool(false)`

Alright guys! This is where we are going to be rounding up for this tutorial post. In our next tutorial, we are going to be discussing about the PHP stats_rand_gen_f() Function.

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