PHP: average functions: Mean (Arithmetic, Geometric, Harmonic) · Median · Mode

See Wiki for detail on mean, median or mode. Please write your own optimizations / implementations in the comments.

function arithmetic_mean($a) {
 return array_sum($a)/count($a);
}

function geometric_mean($a) {
 foreach($a as $i=>$n) $mul = $i == 0 ? $n : $mul*$n;
 return pow($mul,1/count($a));
}

function harmonic_mean($a) {
 $sum = 0;
 foreach($a as $n) $sum += 1 / $n;
 return (1/$sum)*count($a);
}

function median($a) {
 sort($a,SORT_NUMERIC); 
 return (count($a) % 2) ? 
  $a[floor(count($a)/2)] : 
  ($a[floor(count($a)/2)] + $a[floor(count($a)/2) - 1]) / 2;
}

function modal_score($a) {
 $quant = array();
 foreach($a as $n) $quant["$n"]++;
 $max = 0;
 $mode = 0;
 foreach($quant as $key=>$n) {
  if($n>$max) {
   $max = $n;
   $mode = $key;
  }
 }
 return $mode;
}