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# 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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