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PHP : Function Reference : Statistics Functions : stats_standard_deviation

stats_standard_deviation

Returns the standard deviation (PECL stats:1.0.0-1.0.2)
float stats_standard_deviation ( array a [, bool sample] )


Code Examples / Notes » stats_standard_deviation

kotecky o hotmail o com

Missing standard deviation calculated from a population (division by N or by N-1): http://en.wikipedia.org/wiki/Standard_deviation

mightymrj

Here's a couple functions I made that easily calculate the standard deviation.  
function average($array){
$sum   = array_sum($array);
$count = count($array);
return $sum/$count;
}
//The average function can be use independantly but the deviation function uses the average function.
function deviation ($array){

$avg = average($array);
foreach ($array as $value) {
$variance[] = pow($value-$avg, 2);
}
$deviation = sqrt(average($variance));
return $deviation;
}
I hope this is useful


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