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 )

READ: PHP | stats_dens_beta() Function

Parameter Details

Sr.No	Parameter	Description
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)

READ: PHP | stats_dens_chisquare() Function

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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