Hi there,
Bug #24064 (submitted by tularis@php.net) requests a standard deviation
function for PHP. I realise that any of you could implement this in 10
minutes, but according to the bug database it is still Open so I figured I
would give it a try myself!
There are probably a dozen errors in the code and/or places where it could
be better optimised, but I'm hoping one of you might be able to help with
that. So, the attached diff file implements the function array_std_dev(),
to calculate standard deviation using the deviation method.
With the function in place, standard deviation is calculated like this:
<?php
$scores = array(18,5,7,18,3,2,10);
print array_std_dev($score);
// prints 6.6833125519211
?>
My first attempt at implementing this was using an extra array to buffer the
deviations - this was more out of curiosity to see how the array stuff
works. Sadly, it caused PHP to segfault and I couldn't figure out why - can
any of you help me spot the brain fart? (I've attached the offending code
in bad_stddev_code.txt)
Yours,
Paul
PS: I'm not on the internals list, so I would appreciate it if you would CC
me on your reply.
