PHP | stats_covariance() Function

PHP stats_covariance() 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_covariance() Function.

The built-in PHP stats_covariance() function computes the covariance of two data sets. Covariance in it's simple form is described as a measure which computes how much two random variable vary together.

Syntax

Following below is the syntax to use this function -

float stats_covariance( array $a,  array $b )


Parameter Details

Sr.NoParameterDescription
1

a

The first array

2

b

The second array


Return Value

This function returns the covariance of the arrays a and b, otherwise false on failure.

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

The following example below computes the covariance of arrays a and b -

<?php
   $a = array(15, 16, 8, 6, 15, 12, 12, 18, 12, 20, 12, 14);

   $b = array(17.24, 15, 14.91, 4.5, 18, 6.29, 19.23, 18.69, 7.21, 42.06, 7.5, 8);

   var_dump(stats_covariance($a_1, $a_2));
?>

Output

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

float(25.460555555556)

Example2

Following is an error case. In the following example below, we passed two arrays with different sizes. A warning is shown in logs.

<?php
   var_dump(stats_covariance(array(2,1), array(1))); //arrays not of same size
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_covariance(): The data set are not of the same size.

bool(false)

Example3

Following is an error case. In the following example below, we passed two arrays with one of them having zero elements. Warning is displayed in logs.

<?php
   var_dump(stats_covariance(array(), array(0))); //first array with zero elements
?>

Output

The above code will produce the following result and a warning in logs PHP Warning: stats_covariance(): The first array has zero elements.

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_dens_beta() Function.

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