PHP | stats_rand_gen_gamma() Function

PHP stats_rand_gen_gamma() Function


Hello folks! welcome back to a new edition of our tutorial on PHP. In this tutorial guide, we are going to be discussing briefly about the php stats_rand_gen_gamma() function.

The PHP stats_rand_gen_gamma() function is used to generate a random deviate from the gamma distribution.

Syntax

Following below is the syntax to use this function -

float stats_rand_gen_gamma( float $a, float $r )


Parameter Details

Sr.NoParameterDescription
1

a

location parameter of Gamma distribution (a > 0).

2

r

shape parameter of Gamma distribution (r > 0).


Return Value

This function generates a random deviate from the gamma distribution whose density is (A**R)/Gamma(R) * X**(R-1) * Exp(-A*X).

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

Following example computes the random deviation from the gamma distribution -

<?php
   var_dump(is_float(stats_rand_gen_gamma(1, 1)));
?>

Output

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

bool(true)

Example2

The following is an error case. In the below example, we have passed a < 0. A warning is shown in logs -

<?php
   // error case
   var_dump(stats_rand_gen_gamma(-0.1, 1));    // a < 0
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_rand_gen_gamma: A or R nonpositive. A value: -1.000000E-1, R value: 1.000000E+0

bool(false)

Example3

The following is an error case. In the below example, we have passed a == 0. A warning is shown in logs -

<?php
   // error cases
   var_dump(stats_rand_gen_gamma(0, 1));       // a == 0
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_rand_gen_gamma: A or R nonpositive. A value: 0.000000E+0, R value: 1.000000E+0

bool(false)

Example4

The following below is an error case. In the following example, we have passed r < 0. A warning is shown in logs -

<?php
   // error cases
   var_dump(stats_rand_gen_gamma(1, -.1));     // r < 0
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_rand_gen_gamma: A or R nonpositive. A value: 1.000000E+0, R value: -1.000000E-1

bool(false)

Example5

The following is an error case. In the below example, we have passed r == 0. A warning is shown in logs -

<?php
   // error cases
   var_dump(stats_rand_gen_gamma(1, 0));       // r == 0
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_rand_gen_gamma: A or R nonpositive. A value: 1.000000E+0, R value: 0.000000E+0

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 built-in stats_rand_gen_ibinomial() Function in PHP.

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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