# PHP | stats_dens_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_dens_exponential() Function.

The PHP stats_dens_exponential() function is the probability density function (PDF) of the exponential distribution.

## Syntax

Following below is the syntax to use this function -

`float stats_dens_exponential( float \$x,  float \$scale )`

## Parameter Details

Sr.NoParameterDescription
1

x

The value at which the probability density is calculated.

2

scale

The scale of the distribution.

## Return Value

This built-in function returns the probability density at x, where the random variable can follow the exponential distribution of which the scale is scale, or false on failure.

## 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

The following example below computes the probability density for each x -

```<?php
// check for each x
foreach (range(-0.5, 2, 0.5) as \$x) {
var_dump(round(stats_dens_exponential(\$x, 2), 6));
echo "<br>";
}
?>```

#### Output

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

```float(0)
float(0.5)
float(0.3894)
float(0.303265)
float(0.236183)
float(0.18394)```

### Example2

The following example below computes the probability density for each scale -

```<?php
// check for each scale
foreach (range(0.5, 2, 0.5) as \$scale) {
var_dump(round(stats_dens_exponential(1, \$scale), 6));
echo "<br>";
}
?>```

#### Output

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

```float(0.270671)
float(0.367879)
float(0.342278)
float(0.303265)```

### Example3

Following is an error case. In the following example, we passed scale = 0. A warning is shown in logs -

```<?php
// error cases
var_dump(stats_dens_exponential(1, 0)); // scale = 0
?>```

#### Output

The above code will produce the following result and a warning in logs PHP Warning: stats_dens_exponential(): scale == 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_dens_f() Function.

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