# PHP | stats_cdf_poisson() Function

March 20, 2021

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_poisson() Function.

The built-in

The built-in

*stats_cdf_poisson()*function in PHP is used to calculate any one parameter of the poisson distribution given values for the others.## Syntax

Following below is the syntax to use this function -

float stats_cdf_poisson ( float $par1, float $par2, int $which )

## Parameter Details

Sr.No | Parameter | Description |
---|---|---|

1 | par1 | The first parameter |

2 | par2 | The second parameter |

3 | 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 poisson distribution. The kind of the return value and parameters (par1 and par2) are determined by

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

*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.

- lambda denotes the rate parameter of the poisson distribution.

which | Return value | par1 | par2 |
---|---|---|---|

1 | CDF | x | lambda |

2 | x | CDF | lambda |

3 | lambda | x | CDF |

## 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 (S, XLAM).- P is the cumulation from 0 to S of the poisson density. Input range: [0, 1].

- S is the upper limit of cumulation of the poisson density.

- XLAM is the Mean of the poisson density.

<?php // which = 1 : calculate P from (S, XLAM) var_dump(round(stats_cdf_poisson(1, 2, 1), 6)); ?>

#### Output

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

float(0.406006)

### Example2

In the following example below, when

*which = 2*, calculate S from (P, XLAM).- P is the cumulation from 0 to S of the poisson density. Input range: [0, 1].

- S is the upper limit of cumulation of the poisson density.

- XLAM is the Mean of the poisson density.

<?php // which = 2 : calculate A from (P, XLAM) var_dump(round(stats_cdf_poisson(0.40600585, 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 XLAM from (P, S).- P is the cumulation from 0 to S of the poisson density. Input range: [0, 1].

- S is the upper limit of cumulation of the poisson density.

- XLAM is the Mean of the poisson density.

<?php // which = 3 : calculate XLAM from (P, S) var_dump(round(stats_cdf_poisson(0.40600585, 1, 3), 6)); ?>

#### Output

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

float(2)

### Example4

Following is an error case. In the following example below

*which<1*, warning message is displayed in logs.<?php var_dump(stats_cdf_poisson(1, 2, 0)); // which < 1 ?>

#### Output

The above code will produce the following result and a warning in logs

*PHP Warning: stats_cdf_poisson(): Third parameter ought to be in the 1..3 range*.bool(false)

### Example5

Following is an error case. In the following example below

*which>4*, warning message is displayed in logs.<?php var_dump(stats_cdf_poisson(1, 2, 4)); // which > 3 ?>

#### Output

The above code will produce the following result and a warning in logs

*PHP Warning: stats_cdf_poisson(): Third parameter ought to be in the 1..3 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

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*stats_cdf_t()*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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