PHP | stats_cdf_laplace() Function

PHP stats_cdf_laplace() 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_cdf_laplace() Function.

The built-in stats_cdf_laplace() function can be used in calculating any one parameter of the laplace distribution given values for the others.

Syntax

Following below is the syntax to use this function -

float stats_cdf_laplace ( float $par1, float $par2, float $par3, int $which )


Parameter Details

Sr.NoParameterDescription
1

par1

The first parameter

2

par2

The second parameter

3

par3

The third parameter

4

which

The flag to determine what to be calculated


Return Value

This built-in PHP function returns the CDF, its inverse, or one of its parameters of the laplace distribution. The kind of the return value and parameters (par1, par2, and par3) are determined by which.

The following table list the return value and parameters by which.

  • CDF denotes cumulative distribution function.
  • x denotes the value of the random variable.
  • mu denotes the location parameter of the laplace distribution.
  • b denotes the scale parameter of the laplace distribution.

whichReturn valuepar1par2par3
1CDFxmub
2xCDFmub
3muxCDFb
4bxCDFmu

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

In the following example below, when which = 1, calculate P from (X, MEAN, SD).

  • P is the integral from 0 to X of the laplace density. Input range: [0, 1].
  • X is the upper limit of integration of the laplace density. Input range: [0, +infinity].
  • MEAN of the laplace distribution.
  • SD is the Standard Deviation of the laplace density.

<?php
   // which = 1 : calculate P from (X, MEAN, SD)
   var_dump(round(stats_cdf_laplace(0, 1, 2, 1), 6));
?>

Output

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

float(0.303265)

Example2

In the following example below, when which = 2, calculate X from (P, MEAN, SD).

  • P is the integral from 0 to X of the laplace density. Input range: [0, 1].
  • X is the upper limit of integration of the laplace density. Input range: [0, +infinity].
  • MEAN of the laplace distribution.
  • SD is the Standard Deviation of the laplace density.

<?php
   // which = 2 : calculate X from (P, MEAN, SD)
   var_dump(round(stats_cdf_laplace(0.30326533, 1, 2, 2), 6));
?>

Output

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

float(0)

Example3

In the following example below, when which = 3, calculate MEAN from (P, X, SD).

  • P is the integral from 0 to X of the laplace density. Input range: [0, 1].
  • X is the upper limit of integration of the laplace density. Input range: [0, +infinity].
  • MEAN of the laplace distribution.
  • SD is the Standard Deviation of the laplace density.

<?php
   // which = 3 : calculate MEAN from (P, X, SD)
   var_dump(round(stats_cdf_laplace(0.30326533, 0, 2, 3), 6));
?>

Output

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

float(1)

Example4

In the following example below, when which = 4, calculate SD from (P, X, MEAN).

  • P is the integral from 0 to X of the laplace density. Input range: [0, 1].
  • X is the upper limit of integration of the laplace density. Input range: [0, +infinity].
  • MEAN of the laplace distribution.
  • SD is the Standard Deviation of the laplace density.

<?php
   // which = 4 : calculate SD from (P, X, MEAN)
   var_dump(round(stats_cdf_laplace(0.30326533, 0, 1, 4), 6));
?>

Output

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

float(2)

Example5

Following is an error case. In the following example below which<1, warning message is displayed in logs.

<?php
   var_dump(stats_cdf_laplace(0, 1, 2, 0));       // which < 1
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_cdf_laplace(): Fourth parameter ought to be in the 1..4 range.

bool(false)

Example6

Following is an error case. In the following example below which>4, warning message is displayed in logs.

<?php
   var_dump(stats_cdf_laplace(0, 1, 2, 5));      // which > 4
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_cdf_laplace(): Fourth parameter ought to be in the 1..4 range.

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_cdf_logistic() Function.

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