# PHP | stats_cdf_gamma() 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_gamma() Function.

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

## Syntax

Following below is the syntax to use this function -

`float stats_cdf_gamma ( 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 gamma 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.
• k denotes the shape parameter of the gamma distribution.
• theta denotes the scale parameter of the gamma distribution.

whichReturn valuepar1par2par3
1CDFxktheta
2xCDFktheta
3kxCDFtheta
4thetaxCDFk

## 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, SHAPE, SCALE).

• P is the integral from 0 to X of the gamma density. Input range: [0, 1].
• X is the upper limit of integration of the gamma density. Input range: [0, +infinity].
• SHAPE is the shape parameter of the gamma density.
• SCALE is the scale parameter of the gamma density.

```<?php
// which = 1 : calculate P from (X, SHAPE, SCALE)
var_dump(round(stats_cdf_gamma(5, 3, 2, 1), 6));
?>```

#### Output

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

`float(0.456187)`

### Example2

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

• P is the integral from 0 to X of the gamma density. Input range: [0, 1].
• X is the upper limit of integration of the gamma density. Input range: [0, +infinity].
• SHAPE is the shape parameter of the gamma density.
• SCALE is the scale parameter of the gamma density.

```<?php
// which = 2 : calculate X from (P, SHAPE, SCALE)
var_dump(round(stats_cdf_gamma(0.456186884, 3, 2, 2), 6));
?>```

#### Output

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

`float(5)`

### Example3

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

• P is the integral from 0 to X of the gamma density. Input range: [0, 1].
• X is the upper limit of integration of the gamma density. Input range: [0, +infinity].
• SHAPE is the shape parameter of the gamma density.
• SCALE is the scale parameter of the gamma density.

```<?php
// which = 3 : calculate SHAPE from (P, X, SCALE)
var_dump(round(stats_cdf_gamma(0.456186884, 5, 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 SCALE from (P, X, SHAPE).

• P is the integral from 0 to X of the gamma density. Input range: [0, 1].
• X is the upper limit of integration of the gamma density. Input range: [0, +infinity].
• SHAPE is the shape parameter of the gamma density.
• SCALE is the scale parameter of the gamma density.

```<?php
// which = 4 : calculate SCALE from (P, X, SHAPE)
var_dump(round(stats_cdf_gamma(0.456186884, 5, 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_gamma(1, 0, 1, 0));      // which < 1
?>```

#### Output

The above code will produce the following result and a warning in logs PHP Warning: stats_cdf_gamma(): 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_gamma(1, 0, 1, 5));      // which > 4
?>```

#### Output

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

Feel free to ask your questions where necessary and we will attend to them as soon as possible. If this tutorial was helpful to you, you can use the share button to share this tutorial.

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Thanks for reading and bye for now.