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# 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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Thanks for reading and bye for now.