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Author: sdoylum

Regression.php

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+<?php
+/*
+MIT License
+-----------
+
+Copyright (c) 2021 Seyit Düzoylum
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+*/
+class Regression{
+    function mean($values){
+        return array_sum($values) / (float)(count($values));
+    }
+
+    function variance($values)
+    {
+        $num_of_elements = count($values);
+        $variance = 0;
+        $mean = $this->mean($values);
+        foreach($values as $i)
+        {
+            $variance += pow(($i - $mean), 2);
+        }
+
+        return (float)($variance);
+    }
+
+    function covariance($arr1, $arr2)
+    {
+        $n=count($arr1);
+        $sum = 0;
+        for($i = 0; $i < $n; $i++){
+            $sum = $sum + ($arr1[$i] - $this->mean($arr1)) * ($arr2[$i] - $this->mean($arr2));
+        }
+        return $sum;
+    }
+
+    function coefficients($arr1, $arr2){
+        $arr1_mean = $this->mean($arr1);
+        $arr2_mean = $this->mean($arr2);
+        $b1 = $this->covariance($arr1, $arr2)/$this->variance($arr1);
+        $b0 = $arr2_mean - $b1 * $arr1_mean;
+        return (['b0' => $b0, 'b1' => $b1]);
+    }
+
+    function simple_linear_regression($train, $test){
+        $predictions = array();
+        $x = array_column($train, 'x');
+        $y = array_column($train, 'y');
+        $coef = $this->coefficients($x, $y);
+        foreach ($test as $key => $value) {
+            $pred = $coef['b0']+$coef['b1']*$value;
+            array_push($predictions, $pred);
+        }
+        return $predictions;
+    }
+}

Test.php

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+<?php
+
+/*
+MIT License
+-----------
+
+Copyright (c) 2021 Seyit Düzoylum
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+    include "Regression.php";
+    $reg = new Regression();
+    $train = [
+        0 => ['x' => 2.30,
+              'y' => 1.5],
+
+        1 => ['x' => 1.25,
+              'y' => 1],
+
+        3 => ['x' => 1.68,
+              'y' => 0.75],
+
+        4 => ['x' => 0.91,
+              'y' => 1],
+
+        5 => ['x' => 1.08,
+              'y' => 1],
+    ];
+    $test = [2, 1, 1.2, 5, 4.03];
+    print_r ($reg->simple_linear_regression($train, $test));
+
+?>