Statistical trends additional functions and unit tests (#1896)

* PEARSON() and CORREL() are identical functions
* Unit tests for GROWTH() function
* Move GROWTH() function into Statistical\Trends Class

src/PhpSpreadsheet/Calculation/Calculation.php

@@ -1206,7 +1206,7 @@ class Calculation
         ],
         'GROWTH' => [
             'category' => Category::CATEGORY_STATISTICAL,
-            'functionCall' => [Statistical::class, 'GROWTH'],
+            'functionCall' => [Statistical\Trends::class, 'GROWTH'],
             'argumentCount' => '1-4',
         ],
         'HARMEAN' => [
@@ -1897,7 +1897,7 @@ class Calculation
         ],
         'PEARSON' => [
             'category' => Category::CATEGORY_STATISTICAL,
-            'functionCall' => [Statistical::class, 'CORREL'],
+            'functionCall' => [Statistical\Trends::class, 'CORREL'],
             'argumentCount' => '2',
         ],
         'PERCENTILE' => [

src/PhpSpreadsheet/Calculation/Statistical.php

@@ -1544,6 +1544,11 @@ class Statistical
      *
      * Returns values along a predicted exponential Trend
      *
+     * @Deprecated 1.18.0
+     *
+     * @see Statistical\Trends::GROWTH()
+     *      Use the GROWTH() method in the Statistical\Trends class instead
+     *
      * @param mixed[] $yValues Data Series Y
      * @param mixed[] $xValues Data Series X
      * @param mixed[] $newValues Values of X for which we want to find Y
@@ -1553,22 +1558,7 @@ class Statistical
      */
     public static function GROWTH($yValues, $xValues = [], $newValues = [], $const = true)
     {
-        $yValues = Functions::flattenArray($yValues);
-        $xValues = Functions::flattenArray($xValues);
-        $newValues = Functions::flattenArray($newValues);
-        $const = ($const === null) ? true : (bool) Functions::flattenSingleValue($const);
-
-        $bestFitExponential = Trend::calculate(Trend::TREND_EXPONENTIAL, $yValues, $xValues, $const);
-        if (empty($newValues)) {
-            $newValues = $bestFitExponential->getXValues();
-        }
-
-        $returnArray = [];
-        foreach ($newValues as $xValue) {
-            $returnArray[0][] = $bestFitExponential->getValueOfYForX($xValue);
-        }
-
-        return $returnArray;
+        return Trends::GROWTH($yValues, $xValues, $newValues, $const);
     }
 
     /**

src/PhpSpreadsheet/Calculation/Statistical/Trends.php

@@ -132,6 +132,38 @@ class Trends
         return $bestFitLinear->getValueOfYForX($xValue);
     }
 
+    /**
+     * GROWTH.
+     *
+     * Returns values along a predicted exponential Trend
+     *
+     * @param mixed[] $yValues Data Series Y
+     * @param mixed[] $xValues Data Series X
+     * @param mixed[] $newValues Values of X for which we want to find Y
+     * @param bool $const a logical value specifying whether to force the intersect to equal 0
+     *
+     * @return array of float
+     */
+    public static function GROWTH($yValues, $xValues = [], $newValues = [], $const = true)
+    {
+        $yValues = Functions::flattenArray($yValues);
+        $xValues = Functions::flattenArray($xValues);
+        $newValues = Functions::flattenArray($newValues);
+        $const = ($const === null) ? true : (bool) Functions::flattenSingleValue($const);
+
+        $bestFitExponential = Trend::calculate(Trend::TREND_EXPONENTIAL, $yValues, $xValues, $const);
+        if (empty($newValues)) {
+            $newValues = $bestFitExponential->getXValues();
+        }
+
+        $returnArray = [];
+        foreach ($newValues as $xValue) {
+            $returnArray[0][] = [$bestFitExponential->getValueOfYForX($xValue)];
+        }
+
+        return $returnArray;
+    }
+
     /**
      * INTERCEPT.
      *

tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
+
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
+use PHPUnit\Framework\TestCase;
+
+class GrowthTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
+    }
+
+    /**
+     * @dataProvider providerGROWTH
+     *
+     * @param mixed $expectedResult
+     */
+    public function testGROWTH($expectedResult, ...$args): void
+    {
+        $result = Statistical::GROWTH(...$args);
+
+        self::assertEqualsWithDelta($expectedResult, $result[0], 1E-12);
+    }
+
+    public function providerGROWTH()
+    {
+        return require 'tests/data/Calculation/Statistical/GROWTH.php';
+    }
+}

tests/data/Calculation/Statistical/GROWTH.php

@@ -0,0 +1,25 @@
+<?php
+
+return [
+    [
+        [
+            [32618.203773539713],
+            [47729.42261474774],
+            [69841.30085621739],
+            [102197.07337883231],
+            [149542.48674004572],
+            [218821.87621459525],
+        ],
+        [33100, 47300, 69000, 102000, 150000, 220000],
+        [11, 12, 13, 14, 15, 16],
+    ],
+    [
+        [
+            [320196.71836347197],
+            [468536.05418404756],
+        ],
+        [33100, 47300, 69000, 102000, 150000, 220000],
+        [11, 12, 13, 14, 15, 16],
+        [17, 18],
+    ],
+];