Basic Moving Aggregation Methods

moving_add.php

<?php

class Aggregate {
    
    public static function avg($value, $index, &$avg) {
        $avg = ($value + $index * $avg) / ($index + 1);
    }
    
    public static function sum($value, $index, &$sum) {
        $sum += $value;
    }
    
    public static function max($value, $index, &$max) {
        if($value > $max) $max = $value;
    }
    
    public static function min($value, $index, &$min) {
        if($value < $min) $min = $value;
    }
    
    public static function stddev($value, $index, &$stddev) {
        $stddev = sqrt((pow($stddev, 2) * $index + pow($value, 2)) / ($index + 1));
    }
    
}