PHP - Develop calculation of average to mean deviation

Question

To calculate average, I was able to coding. here suppose there are a number of figures.

      A
    ======
      6
      3
      3
      4
    ====== 

We know the Average formula is : 1/n*sigma(Ai) so i define in code like:

function calculate_average($arr) {
    $count = count($arr); 
    foreach ($arr as $value) {
        $total = $total + $value;
    }
    $average = ($total/$count);
    return $average;
}

$home_values_array = array("6", "3", "3","4");
$average_home_value = calculate_average($home_values_array);
echo 'Average home value: $'.number_format($average_home_value).'</p>';

My next task is calc mean deviation, here is the formula :

  A    B
==========
  6    8
  3    7
  3    6
  4    5
==========

Mean Dev =  1/n*sigma(|Ai-Bi|) 

My question is how to develop my average code to coding the mean dev calculate, or just simply, how to solve the mean dev code.

Big thanks for the help.

Answer 1

I don't know it's what you need or not.

function calculate($array_1, $array_2){
   $x = 0; $total = 0;

   foreach($array_1 as $element){
      $total += ($element - $array_2[$x]);
      $x++;
   }

   return ($total / count($array_1));
}

echo calculate(array(6, 3, 3, 4), array(8, 7, 6, 5));

Check this link too see how code run. Hope this helps