PHP | stats_cdf_f() Function

PHP stats_cdf_f() 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_f() Function.

The built-in PHP stats_cdf_f() function can be used to calculate any one parameter of f distribution given values for the others.

Syntax

Following below is the syntax to use this function -

float stats_cdf_f ( 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

It returns the CDF, its inverse, or one of its parameters of the F 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.
  • d1 denotes the degree of freedom of the F distribution.
  • d2 denotes the degree of freedom of the F distribution.

whichReturn valuepar1par2par3
1CDFxd1d2
2xCDFd1d2
3d1xCDFd2
4d2xCDFd1

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 (F, DFN, DFD).

  • P is the integral from 0 to F of the f-density. Input range: [0, 1].
  • F is the upper limit of integration of the f-density. Input range: [0, +infinity].
  • DFN is the degree of freedom of the numerator sum of squares.
  • DFD here is the degree of freedom of the denominator sum of squares.

<?php
   // which = 1 : calculate P from (F, DFN, DFD)
   var_dump(round(stats_cdf_f(1, 3, 2, 1), 6));
?>

Output

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

float(0.464758)

Example2

In the following example below, when which = 2, calculate F from (P, DFN, DFD).

  • P is the integral from 0 to F of the f-density. Input range: [0, 1].
  • F is the upper limit of integration of the f-density. Input range: [0, +infinity].
  • DFN is the degree of freedom of the numerator sum of squares.
  • DFD here is the degree of freedom of the denominator sum of squares.

<?php
   // which = 2 : calculate F from (P, DFN, DFD)
   var_dump(round(stats_cdf_f(0.464758002, 3, 2, 2), 6));
?>

Output

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

float(1)

Example3

In the following example below, when which = 3, calculate DFN from (P, F, DFD).

  • P is the integral from 0 to F of the f-density. Input range: [0, 1].
  • F is the upper limit of integration of the f-density. Input range: [0, +infinity].
  • DFN is the degree of freedom of the numerator sum of squares.
  • DFD here is the degree of freedom of the denominator sum of squares.

<?php
   // which = 3 : calculate DFN from (P, F, DFD)
   var_dump(round(stats_cdf_f(0.464758002, 1, 2, 3), 6));
?>

Output

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

float(3)

Example4

In the following example below, when which = 4, calculate DFD from (P, F, DFN).

  • P is the integral from 0 to F of the f-density. Input range: [0, 1].
  • F is the upper limit of integration of the f-density. Input range: [0, +infinity].
  • DFN is the degree of freedom of the numerator sum of squares.
  • DFD here is the degree of freedom of the denominator sum of squares.

<?php
   // which = 4 : calculate DFD from (P, F, DFN)
   var_dump(round(stats_cdf_f(0.464758002, 1, 3, 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_f(1, 3, 2, 0)); // which < 1
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_cdf_f(): 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_f(1, 3, 2, 5));   // which > 4
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_cdf_f(): 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 stats_cdf_gamma() Function in PHP.

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