My brother needed to figure out how to do a “moving average” in some code he was writing a while ago. I’d never done this before and couldn’t find any really simple code examples so ended up on Wikipedia where I found it’s actually called a cumulative moving average.

Super simple code example follows:

<?php $numbers = array(1,2,3,4); // A simple function to calculate averages function average($array) { return (array_sum($array) / count($array)); } /* * Simple function to calculate moving average with the following parameters * $datapoint - the most recently acquired new datapoint * $average - the current average * $count - the total number of items we're dealing with */ function cumulativeAverage($datapoint, $average, $count) { return $average + (($datapoint - $average) / $count); } // First let's print the average calculated normally so we can compare to the final result print "Normal average:\t\t".average($numbers)."\n"; // $lastav stores the most recently calculated average $lastav = 0; // Loop through all the numbers in the array and calculate the cumulative average each time for ($i = 0; $i<sizeof($numbers);$i++) { $lastav = cumulativeAverage($numbers[$i], $lastav, $i+1); } print "Cumulative Average:\t".$lastav."\n"; >>

Funnily enough I’ve had to use a cumulative moving average too. Here’s the method I used to calculate the average tournament bias over 1000’s of tournaments:

`AverageBiasedFinish = ((AverageBiasedFinish*(TourneyCount-1))+BiasedFinish)/TourneyCount`

Your method of finding the difference is neater, however I was also playing around with exponential moving averages like:

`AverageBiasedFinish = ((AverageBiasedFinish*9+BiasedFinish)/10`

thanks it helped me to make it in coffeescript

https://gist.github.com/mikesmullin/6043986