better arguments format for regression

src/Phpml/Math/Matrix.php

@@ -51,6 +51,21 @@ class Matrix
         $this->matrix = $matrix;
     }
 
+    /**
+     * @param array $array
+     * 
+     * @return Matrix
+     */
+    public static function fromFlatArray(array $array)
+    {
+        $matrix = [];
+        foreach ($array as $value) {
+            $matrix[] = [$value];
+        }
+
+        return new self($matrix);
+    }
+
     /**
      * @return array
      */
@@ -115,16 +130,14 @@ class Matrix
         if ($this->rows == 1 && $this->columns == 1) {
             $determinant = $this->matrix[0][0];
         } elseif ($this->rows == 2 && $this->columns == 2) {
-            $determinant = $this->matrix[0][0] * $this->matrix[1][1] -
+            $determinant =
+                $this->matrix[0][0] * $this->matrix[1][1] -
                 $this->matrix[0][1] * $this->matrix[1][0];
         } else {
             for ($j = 0; $j < $this->columns; ++$j) {
                 $subMatrix = $this->crossOut(0, $j);
-                if (fmod($j, 2) == 0) {
+                $minor = $this->matrix[0][$j] * $subMatrix->getDeterminant();
-                    $determinant += $this->matrix[0][$j] * $subMatrix->getDeterminant();
+                $determinant += fmod($j, 2) == 0 ? $minor : -$minor;
-                } else {
-                    $determinant -= $this->matrix[0][$j] * $subMatrix->getDeterminant();
-                }
             }
         }
 

src/Phpml/Regression/LeastSquares.php

@@ -76,8 +76,8 @@ class LeastSquares implements Regression
      */
     private function computeCoefficients()
     {
-        $samplesMatrix = new Matrix($this->samples);
+        $samplesMatrix = $this->getSamplesMatrix();
-        $targetsMatrix = new Matrix($this->targets);
+        $targetsMatrix = $this->getTargetsMatrix();
 
         $ts = $samplesMatrix->transpose()->multiply($samplesMatrix)->inverse();
         $tf = $samplesMatrix->transpose()->multiply($targetsMatrix);
@@ -85,4 +85,32 @@ class LeastSquares implements Regression
         $this->coefficients = $ts->multiply($tf)->getColumnValues(0);
         $this->intercept = array_shift($this->coefficients);
     }
+
+    /**
+     * Add one dimension for intercept calculation.
+     *
+     * @return Matrix
+     */
+    private function getSamplesMatrix()
+    {
+        $samples = [];
+        foreach ($this->samples as $sample) {
+            array_unshift($sample, 1);
+            $samples[] = $sample;
+        }
+
+        return new Matrix($samples);
+    }
+
+    /**
+     * @return Matrix
+     */
+    private function getTargetsMatrix()
+    {
+        if (is_array($this->targets[0])) {
+            return new Matrix($this->targets);
+        }
+
+        return Matrix::fromFlatArray($this->targets);
+    }
 }

tests/Phpml/Regression/LeastSquaresTest.php

@@ -13,8 +13,8 @@ class LeastSquaresTest extends \PHPUnit_Framework_TestCase
         $delta = 0.01;
 
         //https://www.easycalculation.com/analytical/learn-least-square-regression.php
-        $samples = [[1, 60], [1, 61], [1, 62], [1, 63], [1, 65]];
+        $samples = [[60], [61], [62], [63], [65]];
-        $targets = [[3.1], [3.6], [3.8], [4], [4.1]];
+        $targets = [3.1, 3.6, 3.8, 4, 4.1];
 
         $regression = new LeastSquares();
         $regression->train($samples, $targets);
@@ -22,8 +22,8 @@ class LeastSquaresTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals(4.06, $regression->predict([64]), '', $delta);
 
         //http://www.stat.wmich.edu/s216/book/node127.html
-        $samples = [[1, 9300], [1, 10565], [1, 15000], [1, 15000], [1, 17764], [1, 57000], [1, 65940], [1, 73676], [1, 77006], [1, 93739], [1, 146088], [1, 153260]];
+        $samples = [[9300], [10565], [15000], [15000], [17764], [57000], [65940], [73676], [77006], [93739], [146088], [153260]];
-        $targets = [[7100], [15500], [4400], [4400], [5900], [4600], [8800], [2000], [2750], [2550],  [960], [1025]];
+        $targets = [7100, 15500, 4400, 4400, 5900, 4600, 8800, 2000, 2750, 2550,  960, 1025];
 
         $regression = new LeastSquares();
         $regression->train($samples, $targets);
@@ -40,8 +40,8 @@ class LeastSquaresTest extends \PHPUnit_Framework_TestCase
         $delta = 0.01;
 
         //http://www.stat.wmich.edu/s216/book/node129.html
-        $samples = [[1,  73676, 1996], [1,  77006, 1998], [1,  10565, 2000], [1, 146088, 1995], [1,  15000, 2001], [1,  65940, 2000], [1,   9300, 2000], [1,  93739, 1996], [1, 153260, 1994], [1,  17764, 2002], [1,  57000, 1998], [1,  15000, 2000]];
+        $samples = [[73676, 1996], [77006, 1998], [10565, 2000], [146088, 1995], [15000, 2001], [65940, 2000], [9300, 2000], [93739, 1996], [153260, 1994], [17764, 2002], [57000, 1998], [15000, 2000]];
-        $targets = [[2000], [2750], [15500], [960], [4400], [8800], [7100], [2550], [1025], [5900], [4600], [4400]];
+        $targets = [2000, 2750, 15500, 960, 4400, 8800, 7100, 2550, 1025, 5900, 4600, 4400];
 
         $regression = new LeastSquares();
         $regression->train($samples, $targets);