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 )

READ: PHP | stats_cdf_exponential() Function

Parameter Details

Sr.No	Parameter	Description
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.

which	Return value	par1	par2	par3
1	CDF	x	d1	d2
2	x	CDF	d1	d2
3	d1	x	CDF	d2
4	d2	x	CDF	d1

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)

READ: PHP | stats_cdf_beta() 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 stats_cdf_gamma() Function in PHP.

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Thanks for reading and bye for now.