Linear Regression PHP Class

<?php /** * @author Son Nguyen * @since 11/18/2005 * @package Framework.Data * @subpackage Math */ class CRegressionLinear { private $mDatas; /** constructor */ function __construct($pDatas) { $this->mDatas = $pDatas; } /** get the coefficients */ function calculate() { $n = count($this->mDatas); $vSumXX = $vSumXY = $vSumX = $vSumY = 0; foreach ($this->mDatas AS $x=>$y) { $vSumXY += $x*$y; $vSumXX += $x*$x; $vSumX += $x; $vSumY += $y; } // rof $a = ($n*$vSumXY - $vSumX*$vSumY)/($n*$vSumXX - $vSumX*$vSumX); $b = ($vSumY - $a*$vSumX)/$n; return array($a,$b); } /** given x, return the prediction */ function predict($x) { list($a,$b) = $this->calculate(); $y = $a*$x+$b; return $y; } } ?>