Fix types and comments, add unit test

Author: insel-maz

src/Statistics/Regression/Models/MultilinearModel.php

@@ -4,6 +4,9 @@
 
 trait MultilinearModel
 {
+    /**
+     * @var list<string>
+     */
     private static $subscripts = ['₀', '₁', '₂', '₃', '₄', '₅', '₆', '₇', '₈', '₉'];
 
     /**

src/Statistics/Regression/Multilinear.php

@@ -44,9 +44,14 @@ public function evaluate(float $x): float
      * @param non-empty-list<float> $vector
      *
      * @return float
+     *
+     * @throws BadDataException
      */
     public function evaluateVector(array $vector): float
     {
+        if (empty($this->parameters)) {
+            throw new Exception\BadDataException('Regression parameters are not calculated');
+        }
         return $this->evaluateModel($vector, $this->parameters);
     }
 }

src/Statistics/Regression/Regression.php

@@ -8,8 +8,8 @@
 abstract class Regression
 {
     /**
-     * Array of x and y points: [ [x₁₁, x₁₂, x₁ₖ, y₁], [x₂₁, x₂₂, x₂ₖ, y₂], ... ]
-     * @var list<array{float, float, ...<float>}>
+     * Array of x and y points: [ [ x₁ | [ x₁₁, x₁₂, x₁ₖ ], y₁ ], [ x₂ | [ x₂₁, x₂₂, x₂ₖ ], y₂ ], ... ]
+     * @var list<array{float|non-empty-list<float>, float}>
      */
     protected $points;
 
@@ -91,7 +91,7 @@ public function evaluateVector(array $vector): float
     /**
      * Get points
      *
-     * @return array<array{float, float}>
+     * @return list<array{float|non-empty-list<float>, float}>
      */
     public function getPoints(): array
     {

tests/Statistics/Regression/MultilinearTest.php

@@ -58,8 +58,8 @@ public function dataProviderForParameters(): array
                 // y = 2x₁ - 0.5x₂ + 10
                 // Order from Vandermonde (d=2, p=1): [0,0], [0,1], [1,0]
                 // β₀ = ε = 10
-                // β₁ = x₂ coeff = -0.5
-                // β₂ = x₁ coeff = 2
+                // β₁ = x₁ coeff = 2
+                // β₂ = x₂ coeff = -0.5
                 [
                     [[1, 5], 9.5],   // 2(1) - 0.5(5) + 10 = 2 - 2.5 + 10 = 9.5
                     [[2, 8], 10],    // 2(2) - 0.5(8) + 10 = 4 - 4 + 10 = 10

tests/Statistics/Regression/RegressionTest.php

@@ -263,4 +263,41 @@ public function dataProviderForSumOfSquaresEqualsSumOfSQuaresRegressionPlusSumOf
             [ [[61,105], [62,120], [63,120], [65,160], [65,120], [68,145], [69,175], [70,160], [72,185], [75,210]] ],
         ];
     }
+
+    /**
+     * @test         getXss
+     * @dataProvider dataProviderForXss
+     * @param        array $points
+     * @param        array $expectedXss
+     */
+    public function testXss(array $points, array $expectedXss): void
+    {
+        // Given
+        $regression = new Linear($points);
+
+        // Then
+        $this->assertEqualsWithDelta($expectedXss, $regression->getXss(), 0.00001);
+    }
+
+    /**
+     * @return array
+     */
+    public function dataProviderForXss(): array
+    {
+        $y = 0;
+        return [
+            [
+                [[1, $y], [2, $y], [3, $y]],
+                [[1], [2], [3]],
+            ],
+            [
+                [[[1], $y], [[2], $y], [[3], $y]],
+                [[1], [2], [3]],
+            ],
+            [
+                [[[1, 10], $y], [[2, 20], $y], [[3, 30], $y]],
+                [[1, 10], [2, 20], [3, 30]],
+            ],
+        ];
+    }
 }