From a11e372b3ad4462278cc05be0f46291c5f29285d Mon Sep 17 00:00:00 2001
From: Dennis Eichhorn <spl1nes.com@googlemail.com>
Date: Fri, 25 Dec 2015 13:56:04 +0100
Subject: [PATCH] Implementing linear regresion

---
 Math/Algebra/Regression.php | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 Math/Algebra/Regression.php

diff --git a/Math/Algebra/Regression.php b/Math/Algebra/Regression.php
new file mode 100644
index 000000000..f85023fdf
--- /dev/null
+++ b/Math/Algebra/Regression.php
@@ -0,0 +1,31 @@
+<?php
+namespace phpOMS\Math\Algebra;
+
+class Regression
+{
+    public static function linearRegression(array $x, array $y)
+    {
+        $count = count($x);
+
+        if ($count !== count($y)) {
+            throw new \Exception('Dimensions');
+        }
+
+        $xSum = array_sum($x);
+        $ySum = array_sum($y);
+
+        $xxSum = 0;
+        $xySum = 0;
+
+        for ($i = 0; $i < $count; $i++) {
+
+            $xySum += ($x[$i] * $y[$i]);
+            $xxSum += ($x[$i] * $x[$i]);
+        }
+
+        $m = (($count * $xySum) - ($xSum * $ySum)) / (($count * $xxSum) - ($xSum * $xSum));
+        $b = ($ySum - ($m * $xSum)) / $count;
+
+        return ['m' => $m, 'b' => $b];
+    }
+}