Calculate the mean / average of a set of angles in radians / degrees

mean_of_angles.php

<?php
/*
  From: https://en.wikipedia.org/wiki/Mean_of_circular_quantities
  Parameters:
    $angles: array
    $degrees: boolean. Angles and result in degrees (default)
*/
function mean_of_angles( $angles, $degrees = true ) {
  if ( $degrees ) {
    $angles = array_map("deg2rad", $angles); // Convert to radians
  }
  $s_ = 0;
  $c_ = 0;
  $len = count( $angles );
  for ($i = 0; $i < $len; $i++) {
    $s_ += sin( $angles[$i] );
    $c_ += cos( $angles[$i] );
  }
  // $s_ /= $len;
  // $c_ /= $len;

  $mean = atan2( $s_, $c_ );
  if ( $degrees ) {
    $mean = rad2deg( $mean ); // Convert to degrees
  }
  return $mean;
}

/* Usage */
$angles = [ 355, 5, 15 ];
echo mean_of_angles( $angles ); // Returns 5

?>