note 48783 added to ref.math

Two functions I didn't find elsewhere... one to compute mean of an array of numbers, and another to computer variance of a sample of numbers. Both take an array of numbers as arguments. Not much error checking, or optimization... (note: variance function uses the average function...) <?php function average($arr) { if (!count($arr)) return 0; $sum = 0; for ($i = 0; $i < count($arr); $i++) { $sum += $arr[$i]; } return $sum / count($arr); } function variance($arr) { if (!count($arr)) return 0; $mean = average($arr); $sos = 0; // Sum of squares for ($i = 0; $i < count($arr); $i++) { $sos += ($arr[$i] - $mean) * ($arr[$i] - $mean); } return $sos / (count($arr)-1); // denominator = n-1; i.e. estimating based on sample // n-1 is also what MS Excel takes by default in the // VAR function } echo variance(array(4,6,23,15,18)); // echoes 64.7...correct value :) ?> ---- Manual Page -- http://www.php.net/manual/en/ref.math.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+48783 Delete -- http://master.php.net/manage/user-notes.php?action=delete+48783&report=yes Reason: bad code -- http://master.php.net/manage/user-notes.php?action=delete+48783&report=yes&reason=bad+code Reason: spam -- http://master.php.net/manage/user-notes.php?action=delete+48783&report=yes&reason=spam Reason: useless example -- http://master.php.net/manage/user-notes.php?action=delete+48783&report=yes&reason=useless+example Reason: contains commercial links -- http://master.php.net/manage/user-notes.php?action=delete+48783&report=yes&reason=contains+commercial+links Reason: useless note -- http://master.php.net/manage/user-notes.php?action=delete+48783&report=yes&reason=useless+note Reject -- http://master.php.net/manage/user-notes.php?action=reject+48783&report=yes Search -- http://master.php.net/manage/user-notes.php