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BioPHP - Variance

Original code submitted by joseba
Code bellow is covered by GNU GPL v2 license.

Description

Last change: 2010/10/18 17:04 | Edit description | Recent Changes | Original description

Calculates varience of a serie of numbers

Code

Last change: 2010/10/18 17:04 | Edit Code | Recent Changes | Download | Original code

// This function will only process a one dimensional array
function variance( $data ) {
  $num_elements                 = num_elements( $data );
  $sum                         = 0;
  $numValidElements        = 0;

  $mean = mean( $data );


  for($i=0; $i < $num_elements; $i++ ) {
    if(  isset( $data[$i] )  ) {
      $tmp = $data[$i] - $mean;
      $sum += $tmp * $tmp;
      $numValidElements += 1; 
    }
  }

  $variance = $sum / ( $numValidElements - 1 );

  return $variance;
}