From 459d27c7c81fe39f8f59d44734a5593e0b21c032 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 20:39:51 +0100
Subject: [PATCH 01/18] - Move TREND() functions into the Statistical Trends
 class - Unit tests forTREND() - Create Confidence class for Statistical
 Confidence functions

---
 .../Calculation/Calculation.php               |  6 +--
 .../Calculation/Statistical.php               | 22 +++-------
 .../Calculation/Statistical/Confidence.php    | 41 +++++++++++++++++++
 .../Calculation/Statistical/Trends.php        | 32 +++++++++++++++
 .../Functions/Statistical/TrendTest.php       | 32 +++++++++++++++
 tests/data/Calculation/Statistical/TREND.php  | 16 ++++++++
 6 files changed, 130 insertions(+), 19 deletions(-)
 create mode 100644 src/PhpSpreadsheet/Calculation/Statistical/Confidence.php
 create mode 100644 tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
 create mode 100644 tests/data/Calculation/Statistical/TREND.php

diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index 04b8ffab9f..0d06f04eaa 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -579,12 +579,12 @@ class Calculation
         ],
         'CONFIDENCE' => [
             'category' => Category::CATEGORY_STATISTICAL,
-            'functionCall' => [Statistical::class, 'CONFIDENCE'],
+            'functionCall' => [Statistical\Confidence::class, 'CONFIDENCE'],
             'argumentCount' => '3',
         ],
         'CONFIDENCE.NORM' => [
             'category' => Category::CATEGORY_STATISTICAL,
-            'functionCall' => [Statistical::class, 'CONFIDENCE'],
+            'functionCall' => [Statistical\Confidence::class, 'CONFIDENCE'],
             'argumentCount' => '3',
         ],
         'CONFIDENCE.T' => [
@@ -2454,7 +2454,7 @@ class Calculation
         ],
         'TREND' => [
             'category' => Category::CATEGORY_STATISTICAL,
-            'functionCall' => [Statistical::class, 'TREND'],
+            'functionCall' => [Statistical\Trends::class, 'TREND'],
             'argumentCount' => '1-4',
         ],
         'TRIM' => [
diff --git a/src/PhpSpreadsheet/Calculation/Statistical.php b/src/PhpSpreadsheet/Calculation/Statistical.php
index 4b5c8094d0..6ae8564d87 100644
--- a/src/PhpSpreadsheet/Calculation/Statistical.php
+++ b/src/PhpSpreadsheet/Calculation/Statistical.php
@@ -2941,6 +2941,11 @@ public static function TINV($probability, $degrees)
      *
      * Returns values along a linear Trend
      *
+     * @Deprecated 1.18.0
+     *
+     * @see Statistical\Trends::TREND()
+     *      Use the TREND() method in the Statistical\Trends class instead
+     *
      * @param mixed[] $yValues Data Series Y
      * @param mixed[] $xValues Data Series X
      * @param mixed[] $newValues Values of X for which we want to find Y
@@ -2950,22 +2955,7 @@ public static function TINV($probability, $degrees)
      */
     public static function TREND($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);
-
-        $bestFitLinear = Trend::calculate(Trend::TREND_LINEAR, $yValues, $xValues, $const);
-        if (empty($newValues)) {
-            $newValues = $bestFitLinear->getXValues();
-        }
-
-        $returnArray = [];
-        foreach ($newValues as $xValue) {
-            $returnArray[0][] = $bestFitLinear->getValueOfYForX($xValue);
-        }
-
-        return $returnArray;
+        return Trends::TREND($yValues, $xValues, $newValues, $const);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Calculation/Statistical/Confidence.php b/src/PhpSpreadsheet/Calculation/Statistical/Confidence.php
new file mode 100644
index 0000000000..c4c2a7dd91
--- /dev/null
+++ b/src/PhpSpreadsheet/Calculation/Statistical/Confidence.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical;
+
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
+
+class Confidence
+{
+    /**
+     * CONFIDENCE.
+     *
+     * Returns the confidence interval for a population mean
+     *
+     * @param float $alpha
+     * @param float $stdDev Standard Deviation
+     * @param float $size
+     *
+     * @return float|string
+     */
+    public static function CONFIDENCE($alpha, $stdDev, $size)
+    {
+        $alpha = Functions::flattenSingleValue($alpha);
+        $stdDev = Functions::flattenSingleValue($stdDev);
+        $size = Functions::flattenSingleValue($size);
+
+        if ((is_numeric($alpha)) && (is_numeric($stdDev)) && (is_numeric($size))) {
+            $size = floor($size);
+            if (($alpha <= 0) || ($alpha >= 1)) {
+                return Functions::NAN();
+            }
+            if (($stdDev <= 0) || ($size < 1)) {
+                return Functions::NAN();
+            }
+
+            return Statistical::NORMSINV(1 - $alpha / 2) * $stdDev / sqrt($size);
+        }
+
+        return Functions::VALUE();
+    }
+}
diff --git a/src/PhpSpreadsheet/Calculation/Statistical/Trends.php b/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
index 23bffced43..d06214de2f 100644
--- a/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
+++ b/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
@@ -388,4 +388,36 @@ public static function STEYX($yValues, $xValues)
 
         return $bestFitLinear->getStdevOfResiduals();
     }
+
+    /**
+     * TREND.
+     *
+     * Returns values along a linear 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 $const a logical value specifying whether to force the intersect to equal 0
+     *
+     * @return array of float
+     */
+    public static function TREND($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);
+
+        $bestFitLinear = Trend::calculate(Trend::TREND_LINEAR, $yValues, $xValues, $const);
+        if (empty($newValues)) {
+            $newValues = $bestFitLinear->getXValues();
+        }
+
+        $returnArray = [];
+        foreach ($newValues as $xValue) {
+            $returnArray[0][] = [$bestFitLinear->getValueOfYForX($xValue)];
+        }
+
+        return $returnArray;
+    }
 }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
new file mode 100644
index 0000000000..d3388cdb39
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.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 TrendTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
+    }
+
+    /**
+     * @dataProvider providerGROWTH
+     *
+     * @param mixed $expectedResult
+     */
+    public function testTREND($expectedResult, ...$args): void
+    {
+        $result = Statistical::TREND(...$args);
+
+        self::assertEqualsWithDelta($expectedResult, $result[0], 1E-12);
+    }
+
+    public function providerGROWTH()
+    {
+        return require 'tests/data/Calculation/Statistical/TREND.php';
+    }
+}
diff --git a/tests/data/Calculation/Statistical/TREND.php b/tests/data/Calculation/Statistical/TREND.php
new file mode 100644
index 0000000000..e9f0106cf8
--- /dev/null
+++ b/tests/data/Calculation/Statistical/TREND.php
@@ -0,0 +1,16 @@
+<?php
+
+return [
+    [
+        [
+            [146171.51515151517],
+            [147189.69696969696],
+            [148207.87878787878],
+            [149226.0606060606],
+            [150244.24242424243]
+        ],
+        [133890, 135000, 135790, 137300, 138130, 139100, 139900, 141120, 141890, 143230, 144000, 145290],
+        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
+        [13, 14, 15, 16, 17],
+    ],
+];
\ No newline at end of file

From 6e5011b20756e8df5d91ac1b23f8cf8216faf17d Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 20:41:16 +0100
Subject: [PATCH 02/18] PHPCS

---
 tests/data/Calculation/Statistical/TREND.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/data/Calculation/Statistical/TREND.php b/tests/data/Calculation/Statistical/TREND.php
index e9f0106cf8..a830954613 100644
--- a/tests/data/Calculation/Statistical/TREND.php
+++ b/tests/data/Calculation/Statistical/TREND.php
@@ -7,10 +7,10 @@
             [147189.69696969696],
             [148207.87878787878],
             [149226.0606060606],
-            [150244.24242424243]
+            [150244.24242424243],
         ],
         [133890, 135000, 135790, 137300, 138130, 139100, 139900, 141120, 141890, 143230, 144000, 145290],
         [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
         [13, 14, 15, 16, 17],
     ],
-];
\ No newline at end of file
+];

From c1634ce05a7d8fede471ac7c0fd3c34865a9c84d Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 20:59:00 +0100
Subject: [PATCH 03/18] Keep Scrutinizer happy

---
 .../Calculation/Functions/Statistical/GrowthTest.php         | 5 +++--
 .../Calculation/Functions/Statistical/TrendTest.php          | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php
index ce4eef8a23..6e1cf7bfa4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php
@@ -17,10 +17,11 @@ protected function setUp(): void
      * @dataProvider providerGROWTH
      *
      * @param mixed $expectedResult
+     * @param mixed $yValues
      */
-    public function testGROWTH($expectedResult, ...$args): void
+    public function testGROWTH($expectedResult, $yValues, ...$args): void
     {
-        $result = Statistical::GROWTH(...$args);
+        $result = Statistical::GROWTH($yValues, ...$args);
 
         self::assertEqualsWithDelta($expectedResult, $result[0], 1E-12);
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
index d3388cdb39..b4f756b579 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
@@ -17,10 +17,11 @@ protected function setUp(): void
      * @dataProvider providerGROWTH
      *
      * @param mixed $expectedResult
+     * @param mixed $yValues
      */
-    public function testTREND($expectedResult, ...$args): void
+    public function testTREND($expectedResult, $yValues, ...$args): void
     {
-        $result = Statistical::TREND(...$args);
+        $result = Statistical::TREND($yValues, ...$args);
 
         self::assertEqualsWithDelta($expectedResult, $result[0], 1E-12);
     }

From 1e1a8b5b384b07a53a725a56ad7d1343cdff6688 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 21:07:27 +0100
Subject: [PATCH 04/18] Make Scrutinizer even happier

---
 tests/PhpSpreadsheetTests/Shared/FontTest.php | 15 +++++++++------
 tests/PhpSpreadsheetTests/Style/ColorTest.php | 15 +++++++++------
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/tests/PhpSpreadsheetTests/Shared/FontTest.php b/tests/PhpSpreadsheetTests/Shared/FontTest.php
index 94ab74b632..bc917654ca 100644
--- a/tests/PhpSpreadsheetTests/Shared/FontTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/FontTest.php
@@ -41,10 +41,11 @@ public function testSetAutoSizeMethodWithInvalidValue(): void
      * @dataProvider providerFontSizeToPixels
      *
      * @param mixed $expectedResult
+     * @param mixed $size
      */
-    public function testFontSizeToPixels($expectedResult, ...$args): void
+    public function testFontSizeToPixels($expectedResult, $size): void
     {
-        $result = Font::fontSizeToPixels(...$args);
+        $result = Font::fontSizeToPixels($size);
         self::assertEquals($expectedResult, $result);
     }
 
@@ -57,10 +58,11 @@ public function providerFontSizeToPixels()
      * @dataProvider providerInchSizeToPixels
      *
      * @param mixed $expectedResult
+     * @param mixed $size
      */
-    public function testInchSizeToPixels($expectedResult, ...$args): void
+    public function testInchSizeToPixels($expectedResult, $size): void
     {
-        $result = Font::inchSizeToPixels(...$args);
+        $result = Font::inchSizeToPixels($size);
         self::assertEquals($expectedResult, $result);
     }
 
@@ -73,10 +75,11 @@ public function providerInchSizeToPixels()
      * @dataProvider providerCentimeterSizeToPixels
      *
      * @param mixed $expectedResult
+     * @param mixed $size
      */
-    public function testCentimeterSizeToPixels($expectedResult, ...$args): void
+    public function testCentimeterSizeToPixels($expectedResult, $size): void
     {
-        $result = Font::centimeterSizeToPixels(...$args);
+        $result = Font::centimeterSizeToPixels($size);
         self::assertEquals($expectedResult, $result);
     }
 
diff --git a/tests/PhpSpreadsheetTests/Style/ColorTest.php b/tests/PhpSpreadsheetTests/Style/ColorTest.php
index 04028f871f..2c017ff4eb 100644
--- a/tests/PhpSpreadsheetTests/Style/ColorTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ColorTest.php
@@ -11,10 +11,11 @@ class ColorTest extends TestCase
      * @dataProvider providerColorGetRed
      *
      * @param mixed $expectedResult
+     * @param mixed $color
      */
-    public function testGetRed($expectedResult, ...$args): void
+    public function testGetRed($expectedResult, $color, ...$args): void
     {
-        $result = Color::getRed(...$args);
+        $result = Color::getRed($color, ...$args);
         self::assertEquals($expectedResult, $result);
     }
 
@@ -27,10 +28,11 @@ public function providerColorGetRed()
      * @dataProvider providerColorGetGreen
      *
      * @param mixed $expectedResult
+     * @param mixed $color
      */
-    public function testGetGreen($expectedResult, ...$args): void
+    public function testGetGreen($expectedResult, $color, ...$args): void
     {
-        $result = Color::getGreen(...$args);
+        $result = Color::getGreen($color, ...$args);
         self::assertEquals($expectedResult, $result);
     }
 
@@ -43,10 +45,11 @@ public function providerColorGetGreen()
      * @dataProvider providerColorGetBlue
      *
      * @param mixed $expectedResult
+     * @param mixed $color
      */
-    public function testGetBlue($expectedResult, ...$args): void
+    public function testGetBlue($expectedResult, $color, ...$args): void
     {
-        $result = Color::getBlue(...$args);
+        $result = Color::getBlue($color, ...$args);
         self::assertEquals($expectedResult, $result);
     }
 

From 877d14be5b59321cb7012731df9643ca8283f64f Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 21:25:46 +0100
Subject: [PATCH 05/18] Deprecate the old CONFIDENCE() method

---
 .../Calculation/Statistical.php               | 24 ++++++-------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/src/PhpSpreadsheet/Calculation/Statistical.php b/src/PhpSpreadsheet/Calculation/Statistical.php
index 6ae8564d87..8a9e3fea33 100644
--- a/src/PhpSpreadsheet/Calculation/Statistical.php
+++ b/src/PhpSpreadsheet/Calculation/Statistical.php
@@ -4,6 +4,7 @@
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Averages;
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Conditional;
+use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Confidence;
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Counts;
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Maximum;
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Minimum;
@@ -832,6 +833,11 @@ public static function CHIINV($probability, $degrees)
      *
      * Returns the confidence interval for a population mean
      *
+     * @Deprecated 1.18.0
+     *
+     * @see Statistical\Confidence::CONFIDENCE()
+     *      Use the CONFIDENCE() method in the Statistical\Confidence class instead
+     *
      * @param float $alpha
      * @param float $stdDev Standard Deviation
      * @param float $size
@@ -840,23 +846,7 @@ public static function CHIINV($probability, $degrees)
      */
     public static function CONFIDENCE($alpha, $stdDev, $size)
     {
-        $alpha = Functions::flattenSingleValue($alpha);
-        $stdDev = Functions::flattenSingleValue($stdDev);
-        $size = Functions::flattenSingleValue($size);
-
-        if ((is_numeric($alpha)) && (is_numeric($stdDev)) && (is_numeric($size))) {
-            $size = floor($size);
-            if (($alpha <= 0) || ($alpha >= 1)) {
-                return Functions::NAN();
-            }
-            if (($stdDev <= 0) || ($size < 1)) {
-                return Functions::NAN();
-            }
-
-            return self::NORMSINV(1 - $alpha / 2) * $stdDev / sqrt($size);
-        }
-
-        return Functions::VALUE();
+        return Confidence::CONFIDENCE($alpha, $stdDev, $size);
     }
 
     /**

From d3ba7fd5b1fad2ceb7052a20d3d63a90528116e1 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 21:32:19 +0100
Subject: [PATCH 06/18] Additional test case for TREND()

---
 tests/data/Calculation/Statistical/TREND.php | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tests/data/Calculation/Statistical/TREND.php b/tests/data/Calculation/Statistical/TREND.php
index a830954613..418367b2e5 100644
--- a/tests/data/Calculation/Statistical/TREND.php
+++ b/tests/data/Calculation/Statistical/TREND.php
@@ -1,6 +1,24 @@
 <?php
 
 return [
+    [
+        [
+            [133953.33333333334],
+            [134971.51515151517],
+            [135989.69696969696],
+            [137007.87878787878],
+            [138026.0606060606],
+            [139044.24242424243],
+            [140062.42424242425],
+            [141080.60606060608],
+            [142098.78787878787],
+            [143116.9696969697],
+            [144135.15151515152],
+            [145153.33333333334],
+        ],
+        [133890, 135000, 135790, 137300, 138130, 139100, 139900, 141120, 141890, 143230, 144000, 145290],
+        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
+    ],
     [
         [
             [146171.51515151517],

From 055e3410970ececab4c46444d5bb350bb8728b18 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Thu, 4 Mar 2021 23:45:56 +0100
Subject: [PATCH 07/18] Unit tests from Shared Trend classes

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php   |  2 +-
 .../Shared/Trend/LinearBestFitTest.php        | 43 +++++++++++++++++++
 tests/data/Shared/Trend/LinearBestFit.php     | 11 +++++
 3 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
 create mode 100644 tests/data/Shared/Trend/LinearBestFit.php

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index c94997226b..69fa81dabd 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -451,7 +451,7 @@ public function __construct($yValues, $xValues = [], $const = true)
         //    Define X Values if necessary
         if ($nX == 0) {
             $xValues = range(1, $nY);
-        } elseif ($nY != $nX) {
+        } elseif ($nY !== $nX) {
             //    Ensure both arrays of points are the same size
             $this->error = true;
         }
diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
new file mode 100644
index 0000000000..12f63c5b73
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Shared\Trend;
+
+use PhpOffice\PhpSpreadsheet\Shared\Trend\LinearBestFit;
+use PHPUnit\Framework\TestCase;
+
+class LinearBestFitTest extends TestCase
+{
+    /**
+     * @dataProvider providerLinearBestFit
+     *
+     * @param mixed $expectedSlope
+     * @param mixed $expectedIntersect
+     * @param mixed $expectedGoodnessOfFit
+     * @param mixed $yValues
+     * @param mixed $xValues
+     */
+    public function testCodePageNumberToName(
+        $expectedSlope,
+        $expectedIntersect,
+        $expectedGoodnessOfFit,
+        $yValues,
+        $xValues
+    ): void {
+        $bestFit = new LinearBestFit($yValues, $xValues);
+        $slope = $bestFit->getSlope(1);
+        self::assertEquals($expectedSlope[0], $slope);
+        $slope = $bestFit->getSlope();
+        self::assertEquals($expectedSlope[1], $slope);
+        $intersect = $bestFit->getIntersect(1);
+        self::assertEquals($expectedIntersect[0], $intersect);
+        $intersect = $bestFit->getIntersect();
+        self::assertEquals($expectedIntersect[1], $intersect);
+        self::assertSame($expectedGoodnessOfFit[0], $bestFit->getGoodnessOfFit(6));
+        self::assertSame($expectedGoodnessOfFit[1], $bestFit->getGoodnessOfFit());
+    }
+
+    public function providerLinearBestFit()
+    {
+        return require 'tests/data/Shared/Trend/LinearBestFit.php';
+    }
+}
diff --git a/tests/data/Shared/Trend/LinearBestFit.php b/tests/data/Shared/Trend/LinearBestFit.php
new file mode 100644
index 0000000000..43c68151c5
--- /dev/null
+++ b/tests/data/Shared/Trend/LinearBestFit.php
@@ -0,0 +1,11 @@
+<?php
+
+return [
+    [
+        'slope' => [-1.1, -1.1064189189190],
+        'intersect' => [14.1, 14.081081081081],
+        'goodnessOfFit' => [0.873138, 0.8731378215564962],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+    ],
+];

From 9568a3745aea381c03b4d2e9326d7bc20d9e3be6 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Fri, 5 Mar 2021 16:37:53 +0100
Subject: [PATCH 08/18] Unit tests from Shared Trend classes

---
 .../Calculation/Statistical/Trends.php        |  4 +-
 .../Shared/Trend/ExponentialBestFit.php       | 16 ++-
 .../Shared/Trend/LogarithmicBestFit.php       | 18 ++--
 .../Shared/Trend/PowerBestFit.php             | 30 +++---
 .../Functions/Statistical/LogEstTest.php      |  2 +-
 .../Shared/Trend/ExponentialBestFitTest.php   | 49 ++++++++++
 .../Shared/Trend/LinearBestFitTest.php        |  8 +-
 tests/data/Calculation/Statistical/LINEST.php | 97 ++++++++++++++-----
 tests/data/Calculation/Statistical/LOGEST.php | 42 ++++++++
 .../data/Shared/Trend/ExponentialBestFit.php  | 12 +++
 tests/data/Shared/Trend/LinearBestFit.php     |  1 +
 11 files changed, 215 insertions(+), 64 deletions(-)
 create mode 100644 tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php
 create mode 100644 tests/data/Shared/Trend/ExponentialBestFit.php

diff --git a/src/PhpSpreadsheet/Calculation/Statistical/Trends.php b/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
index d06214de2f..a1137cefc1 100644
--- a/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
+++ b/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
@@ -226,7 +226,7 @@ public static function LINEST($yValues, $xValues = null, $const = true, $stats =
                 ],
                 [
                     $bestFitLinear->getSlopeSE(),
-                    $bestFitLinear->getIntersectSE(),
+                    ($const === false) ? Functions::NA() : $bestFitLinear->getIntersectSE(),
                 ],
                 [
                     $bestFitLinear->getGoodnessOfFit(),
@@ -293,7 +293,7 @@ public static function LOGEST($yValues, $xValues = null, $const = true, $stats =
                 ],
                 [
                     $bestFitExponential->getSlopeSE(),
-                    $bestFitExponential->getIntersectSE(),
+                    ($const === false) ? Functions::NA() : $bestFitExponential->getIntersectSE(),
                 ],
                 [
                     $bestFitExponential->getGoodnessOfFit(),
diff --git a/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php b/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
index 82866dee80..f5feb803a4 100644
--- a/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
@@ -92,16 +92,14 @@ public function getIntersect($dp = 0)
      */
     private function exponentialRegression($yValues, $xValues, $const): void
     {
-        foreach ($yValues as &$value) {
-            if ($value < 0.0) {
-                $value = 0 - log(abs($value));
-            } elseif ($value > 0.0) {
-                $value = log($value);
-            }
-        }
-        unset($value);
+        $adjustedYValues = array_map(
+            function ($value) {
+                return ($value < 0.0) ? 0 - log(abs($value)) : log($value);
+            },
+            $yValues
+        );
 
-        $this->leastSquareFit($yValues, $xValues, $const);
+        $this->leastSquareFit($adjustedYValues, $xValues, $const);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php b/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
index c469067d47..404151b5e9 100644
--- a/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
@@ -48,7 +48,7 @@ public function getEquation($dp = 0)
         $slope = $this->getSlope($dp);
         $intersect = $this->getIntersect($dp);
 
-        return 'Y = ' . $intersect . ' + ' . $slope . ' * log(X)';
+        return 'Y = ' . $slope . ' * log(' . $intersect . ' * X)';
     }
 
     /**
@@ -60,16 +60,14 @@ public function getEquation($dp = 0)
      */
     private function logarithmicRegression($yValues, $xValues, $const): void
     {
-        foreach ($xValues as &$value) {
-            if ($value < 0.0) {
-                $value = 0 - log(abs($value));
-            } elseif ($value > 0.0) {
-                $value = log($value);
-            }
-        }
-        unset($value);
+        $adjustedYValues = array_map(
+            function ($value) {
+                return ($value < 0.0) ? 0 - log(abs($value)) : log($value);
+            },
+            $yValues
+        );
 
-        $this->leastSquareFit($yValues, $xValues, $const);
+        $this->leastSquareFit($adjustedYValues, $xValues, $const);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php b/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
index c53eab6381..f05b826d64 100644
--- a/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
@@ -76,24 +76,20 @@ public function getIntersect($dp = 0)
      */
     private function powerRegression($yValues, $xValues, $const): void
     {
-        foreach ($xValues as &$value) {
-            if ($value < 0.0) {
-                $value = 0 - log(abs($value));
-            } elseif ($value > 0.0) {
-                $value = log($value);
-            }
-        }
-        unset($value);
-        foreach ($yValues as &$value) {
-            if ($value < 0.0) {
-                $value = 0 - log(abs($value));
-            } elseif ($value > 0.0) {
-                $value = log($value);
-            }
-        }
-        unset($value);
+        $adjustedYValues = array_map(
+            function ($value) {
+                return ($value < 0.0) ? 0 - log(abs($value)) : log($value);
+            },
+            $yValues
+        );
+        $adjustedXValues = array_map(
+            function ($value) {
+                return ($value < 0.0) ? 0 - log(abs($value)) : log($value);
+            },
+            $xValues
+        );
 
-        $this->leastSquareFit($yValues, $xValues, $const);
+        $this->leastSquareFit($adjustedYValues, $adjustedXValues, $const);
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php
index 4d926f7620..2b2d1ecf12 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php
@@ -19,7 +19,7 @@ class LogEstTest extends TestCase
     public function testLOGEST($expectedResult, $yValues, $xValues, $const, $stats): void
     {
         $result = Statistical::LOGEST($yValues, $xValues, $const, $stats);
-
+        //var_dump($result);
         $elements = count($expectedResult);
         for ($element = 0; $element < $elements; ++$element) {
             self::assertEqualsWithDelta($expectedResult[$element], $result[$element], 1E-12);
diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php
new file mode 100644
index 0000000000..32fa9d3187
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Shared\Trend;
+
+use PhpOffice\PhpSpreadsheet\Shared\Trend\ExponentialBestFit;
+use PHPUnit\Framework\TestCase;
+
+class ExponentialBestFitTest extends TestCase
+{
+    /**
+     * @dataProvider providerExponentialBestFit
+     *
+     * @param mixed $expectedSlope
+     * @param mixed $expectedIntersect
+     * @param mixed $expectedGoodnessOfFit
+     * @param mixed $yValues
+     * @param mixed $xValues
+     * @param mixed $expectedEquation
+     */
+    public function testExponentialBestFit(
+        $expectedSlope,
+        $expectedIntersect,
+        $expectedGoodnessOfFit,
+        $expectedEquation,
+        $yValues,
+        $xValues
+    ): void {
+        $bestFit = new ExponentialBestFit($yValues, $xValues);
+        $slope = $bestFit->getSlope(1);
+        self::assertEquals($expectedSlope[0], $slope);
+        $slope = $bestFit->getSlope();
+        self::assertEquals($expectedSlope[1], $slope);
+        $intersect = $bestFit->getIntersect(1);
+        self::assertEquals($expectedIntersect[0], $intersect);
+        $intersect = $bestFit->getIntersect();
+        self::assertEquals($expectedIntersect[1], $intersect);
+
+        $equation = $bestFit->getEquation(2);
+        self::assertEquals($expectedEquation, $equation);
+
+        self::assertSame($expectedGoodnessOfFit[0], $bestFit->getGoodnessOfFit(6));
+        self::assertSame($expectedGoodnessOfFit[1], $bestFit->getGoodnessOfFit());
+    }
+
+    public function providerExponentialBestFit()
+    {
+        return require 'tests/data/Shared/Trend/ExponentialBestFit.php';
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
index 12f63c5b73..02b82038c0 100644
--- a/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
@@ -15,11 +15,13 @@ class LinearBestFitTest extends TestCase
      * @param mixed $expectedGoodnessOfFit
      * @param mixed $yValues
      * @param mixed $xValues
+     * @param mixed $expectedEquation
      */
-    public function testCodePageNumberToName(
+    public function testLinearBestFit(
         $expectedSlope,
         $expectedIntersect,
         $expectedGoodnessOfFit,
+        $expectedEquation,
         $yValues,
         $xValues
     ): void {
@@ -32,6 +34,10 @@ public function testCodePageNumberToName(
         self::assertEquals($expectedIntersect[0], $intersect);
         $intersect = $bestFit->getIntersect();
         self::assertEquals($expectedIntersect[1], $intersect);
+
+        $equation = $bestFit->getEquation(2);
+        self::assertEquals($expectedEquation, $equation);
+
         self::assertSame($expectedGoodnessOfFit[0], $bestFit->getGoodnessOfFit(6));
         self::assertSame($expectedGoodnessOfFit[1], $bestFit->getGoodnessOfFit());
     }
diff --git a/tests/data/Calculation/Statistical/LINEST.php b/tests/data/Calculation/Statistical/LINEST.php
index 9bd28ffe29..ff1913bc56 100644
--- a/tests/data/Calculation/Statistical/LINEST.php
+++ b/tests/data/Calculation/Statistical/LINEST.php
@@ -1,6 +1,15 @@
 <?php
 
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+
 return [
+    [
+        [2.310344827586207, 0.0],
+        [1, 9, 5, 7],
+        [0, 4, 2, 3],
+        false,
+        false,
+    ],
     [
         [2.0, 1.0],
         [1, 9, 5, 7],
@@ -8,6 +17,46 @@
         true,
         false,
     ],
+    [
+        [0.600378787879, 0.0],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+        false,
+        false,
+    ],
+    [
+        [-1.1064189189190, 14.081081081081],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+        true,
+        false,
+    ],
+    [
+        [
+            [0.600378787879, 0.0],
+            [0.3130441135917, Functions::NA()],
+            [0.2901220667036, 7.193206086629],
+            [3.6782360429317, 9],
+            [190.3200757575760, 465.679924242424],
+        ],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+        false,
+        true,
+    ],
+    [
+        [
+            [-1.1064189189190, 14.081081081081],
+            [0.1491074289251, 1.083468383961],
+            [0.8731378215565, 1.622464237727],
+            [55.0605598780781, 8],
+            [144.9408783783780, 21.059121621622],
+        ],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+        true,
+        true,
+    ],
     [
         [
             [56.837944664032, 11704.347826086974],
@@ -21,29 +70,29 @@
         true,
         true,
     ],
-    //    [
-    //        [
-    //            [-234.2371645, 2553.21066, 12529.76817, 27.64138737, 52317.83051],
-    //            [13.26801148, 530.6691519, 400.0668382, 5.429374042, 12237.3616],
-    //            [0.996747993, 970.5784629, '#N/A', '#N/A', '#N/A'],
-    //            [459.7536742, 6, '#N/A', '#N/A', '#N/A'],
-    //            [1732393319, 5652135.316, '#N/A', '#N/A', '#N/A'],
-    //        ],
-    //        [142000, 144000, 151000, 150000, 139000, 169000, 126000, 142900, 163000, 169000, 149000],
-    //        [
-    //            [2310, 2, 2, 20],
-    //            [2333, 2, 2, 12],
-    //            [2356, 3, 1.5, 33],
-    //            [2379, 3, 2, 43],
-    //            [2402, 2, 3, 53],
-    //            [2425, 4, 2, 23],
-    //            [2448, 2, 1.5, 99],
-    //            [2471, 2, 2, 34],
-    //            [2494, 3, 3, 23],
-    //            [2517, 4, 4, 55],
-    //            [2540, 2, 3, 22],
+    //        'multi-series' => [
+    //            [
+    //                [-234.2371645, 2553.21066, 12529.76817, 27.64138737, 52317.83051],
+    //                [13.26801148, 530.6691519, 400.0668382, 5.429374042, 12237.3616],
+    //                [0.996747993, 970.5784629, '#N/A', '#N/A', '#N/A'],
+    //                [459.7536742, 6, '#N/A', '#N/A', '#N/A'],
+    //                [1732393319, 5652135.316, '#N/A', '#N/A', '#N/A'],
+    //            ],
+    //            [142000, 144000, 151000, 150000, 139000, 169000, 126000, 142900, 163000, 169000, 149000],
+    //            [
+    //                [2310, 2, 2, 20],
+    //                [2333, 2, 2, 12],
+    //                [2356, 3, 1.5, 33],
+    //                [2379, 3, 2, 43],
+    //                [2402, 2, 3, 53],
+    //                [2425, 4, 2, 23],
+    //                [2448, 2, 1.5, 99],
+    //                [2471, 2, 2, 34],
+    //                [2494, 3, 3, 23],
+    //                [2517, 4, 4, 55],
+    //                [2540, 2, 3, 22],
+    //            ],
+    //            true,
+    //            true,
     //        ],
-    //        true,
-    //        true,
-    //    ],
 ];
diff --git a/tests/data/Calculation/Statistical/LOGEST.php b/tests/data/Calculation/Statistical/LOGEST.php
index be9e4d7252..38a2ff8d75 100644
--- a/tests/data/Calculation/Statistical/LOGEST.php
+++ b/tests/data/Calculation/Statistical/LOGEST.php
@@ -1,5 +1,7 @@
 <?php
 
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+
 return [
     [
         [1.463275628116, 495.304770158727],
@@ -15,4 +17,44 @@
         true,
         false,
     ],
+    [
+        [1.1743674215053, 1.0],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+        false,
+        false,
+    ],
+    [
+        [0.8135120728565, 20.671878197178],
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+        true,
+        false,
+    ],
+    //    [
+    //        [
+    //            [1.174367421505266, 1.0],
+    //            [0.0672620306083, Functions::NA()],
+    //            [0.3881799938732, 1.545563794251],
+    //            [5.7102087376569, 9],
+    //            [13.6403607201119, 21.498906978904],
+    //        ],
+    //        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+    //        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+    //        false,
+    //        true,
+    //    ],
+    //    [
+    //        [
+    //            [0.8135120728565, 20.671878197178],
+    //            [0.0313021171611, 0.227452478657],
+    //            [0.8445875527654, 0.340603858743],
+    //            [43.4759283593386, 8],
+    //            [5.0436854288511, 0.928087908723],
+    //        ],
+    //        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+    //        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+    //        true,
+    //        true,
+    //    ],
 ];
diff --git a/tests/data/Shared/Trend/ExponentialBestFit.php b/tests/data/Shared/Trend/ExponentialBestFit.php
new file mode 100644
index 0000000000..ac1da739c6
--- /dev/null
+++ b/tests/data/Shared/Trend/ExponentialBestFit.php
@@ -0,0 +1,12 @@
+<?php
+
+return [
+    [
+        'slope' => [0.8, 0.813512072856517],
+        'intersect' => [20.7, 20.671878197177865],
+        'goodnessOfFit' => [0.904868, 0.9048681877346413],
+        'equation' => 'Y = 20.67 * 0.81^X',
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+    ],
+];
diff --git a/tests/data/Shared/Trend/LinearBestFit.php b/tests/data/Shared/Trend/LinearBestFit.php
index 43c68151c5..1997d404bd 100644
--- a/tests/data/Shared/Trend/LinearBestFit.php
+++ b/tests/data/Shared/Trend/LinearBestFit.php
@@ -5,6 +5,7 @@
         'slope' => [-1.1, -1.1064189189190],
         'intersect' => [14.1, 14.081081081081],
         'goodnessOfFit' => [0.873138, 0.8731378215564962],
+        'equation' => 'Y = 14.08 + -1.11 * X',
         [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
         [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
     ],

From 31c2968568d238575e355fbf68ed9d67342622f2 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Fri, 5 Mar 2021 18:29:21 +0100
Subject: [PATCH 09/18] Minor typing improvements

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php   | 30 ++++++++-----------
 .../Shared/Trend/ExponentialBestFit.php       |  4 +--
 .../Shared/Trend/LinearBestFit.php            |  4 +--
 .../Shared/Trend/LogarithmicBestFit.php       |  4 +--
 .../Shared/Trend/PolynomialBestFit.php        |  3 +-
 .../Shared/Trend/PowerBestFit.php             |  4 +--
 src/PhpSpreadsheet/Shared/Trend/Trend.php     |  9 +++---
 7 files changed, 25 insertions(+), 33 deletions(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index 69fa81dabd..3a1f0b1a1f 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -348,13 +348,13 @@ protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY,
             $bestFitY = $this->yBestFitValues[$xKey] = $this->getValueOfYForX($xValue);
 
             $SSres += ($this->yValues[$xKey] - $bestFitY) * ($this->yValues[$xKey] - $bestFitY);
-            if ($const) {
+            if ($const === true) {
                 $SStot += ($this->yValues[$xKey] - $meanY) * ($this->yValues[$xKey] - $meanY);
             } else {
                 $SStot += $this->yValues[$xKey] * $this->yValues[$xKey];
             }
             $SScov += ($this->xValues[$xKey] - $meanX) * ($this->yValues[$xKey] - $meanY);
-            if ($const) {
+            if ($const === true) {
                 $SSsex += ($this->xValues[$xKey] - $meanX) * ($this->xValues[$xKey] - $meanX);
             } else {
                 $SSsex += $this->xValues[$xKey] * $this->xValues[$xKey];
@@ -398,9 +398,8 @@ protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY,
     /**
      * @param float[] $yValues
      * @param float[] $xValues
-     * @param bool $const
      */
-    protected function leastSquareFit(array $yValues, array $xValues, $const): void
+    protected function leastSquareFit(array $yValues, array $xValues, bool $const): void
     {
         // calculate sums
         $x_sum = array_sum($xValues);
@@ -413,7 +412,7 @@ protected function leastSquareFit(array $yValues, array $xValues, $const): void
             $xx_sum += $xValues[$i] * $xValues[$i];
             $yy_sum += $yValues[$i] * $yValues[$i];
 
-            if ($const) {
+            if ($const === true) {
                 $mBase += ($xValues[$i] - $meanX) * ($yValues[$i] - $meanY);
                 $mDivisor += ($xValues[$i] - $meanX) * ($xValues[$i] - $meanX);
             } else {
@@ -426,11 +425,7 @@ protected function leastSquareFit(array $yValues, array $xValues, $const): void
         $this->slope = $mBase / $mDivisor;
 
         // calculate intersect
-        if ($const) {
-            $this->intersect = $meanY - ($this->slope * $meanX);
-        } else {
-            $this->intersect = 0;
-        }
+        $this->intersect = ($const === true) ? $meanY - ($this->slope * $meanX) : 0.0;
 
         $this->calculateGoodnessOfFit($x_sum, $y_sum, $xx_sum, $yy_sum, $xy_sum, $meanX, $meanY, $const);
     }
@@ -440,23 +435,22 @@ protected function leastSquareFit(array $yValues, array $xValues, $const): void
      *
      * @param float[] $yValues The set of Y-values for this regression
      * @param float[] $xValues The set of X-values for this regression
-     * @param bool $const
      */
-    public function __construct($yValues, $xValues = [], $const = true)
+    public function __construct($yValues, $xValues = [])
     {
         //    Calculate number of points
-        $nY = count($yValues);
-        $nX = count($xValues);
+        $yValueCount = count($yValues);
+        $xValueCount = count($xValues);
 
         //    Define X Values if necessary
-        if ($nX == 0) {
-            $xValues = range(1, $nY);
-        } elseif ($nY !== $nX) {
+        if ($xValueCount === 0) {
+            $xValues = range(1, $yValueCount);
+        } elseif ($yValueCount !== $xValueCount) {
             //    Ensure both arrays of points are the same size
             $this->error = true;
         }
 
-        $this->valueCount = $nY;
+        $this->valueCount = $yValueCount;
         $this->xValues = $xValues;
         $this->yValues = $yValues;
     }
diff --git a/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php b/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
index f5feb803a4..570a12ab17 100644
--- a/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
@@ -90,7 +90,7 @@ public function getIntersect($dp = 0)
      * @param float[] $xValues The set of X-values for this regression
      * @param bool $const
      */
-    private function exponentialRegression($yValues, $xValues, $const): void
+    private function exponentialRegression(array $yValues, array $xValues, bool $const): void
     {
         $adjustedYValues = array_map(
             function ($value) {
@@ -114,7 +114,7 @@ public function __construct($yValues, $xValues = [], $const = true)
         parent::__construct($yValues, $xValues);
 
         if (!$this->error) {
-            $this->exponentialRegression($yValues, $xValues, $const);
+            $this->exponentialRegression($yValues, $xValues, (bool) $const);
         }
     }
 }
diff --git a/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php b/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php
index 26a562c551..2208447181 100644
--- a/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php
@@ -58,7 +58,7 @@ public function getEquation($dp = 0)
      * @param float[] $xValues The set of X-values for this regression
      * @param bool $const
      */
-    private function linearRegression($yValues, $xValues, $const): void
+    private function linearRegression(array $yValues, array $xValues, bool $const): void
     {
         $this->leastSquareFit($yValues, $xValues, $const);
     }
@@ -75,7 +75,7 @@ public function __construct($yValues, $xValues = [], $const = true)
         parent::__construct($yValues, $xValues);
 
         if (!$this->error) {
-            $this->linearRegression($yValues, $xValues, $const);
+            $this->linearRegression($yValues, $xValues, (bool) $const);
         }
     }
 }
diff --git a/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php b/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
index 404151b5e9..e273263447 100644
--- a/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
@@ -58,7 +58,7 @@ public function getEquation($dp = 0)
      * @param float[] $xValues The set of X-values for this regression
      * @param bool $const
      */
-    private function logarithmicRegression($yValues, $xValues, $const): void
+    private function logarithmicRegression(array $yValues, array $xValues, bool $const): void
     {
         $adjustedYValues = array_map(
             function ($value) {
@@ -82,7 +82,7 @@ public function __construct($yValues, $xValues = [], $const = true)
         parent::__construct($yValues, $xValues);
 
         if (!$this->error) {
-            $this->logarithmicRegression($yValues, $xValues, $const);
+            $this->logarithmicRegression($yValues, $xValues, (bool) $const);
         }
     }
 }
diff --git a/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php b/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
index d959eddb75..1d34e81c19 100644
--- a/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
@@ -178,9 +178,8 @@ private function polynomialRegression($order, $yValues, $xValues): void
      * @param int $order Order of Polynomial for this regression
      * @param float[] $yValues The set of Y-values for this regression
      * @param float[] $xValues The set of X-values for this regression
-     * @param bool $const
      */
-    public function __construct($order, $yValues, $xValues = [], $const = true)
+    public function __construct($order, $yValues, $xValues = [])
     {
         parent::__construct($yValues, $xValues);
 
diff --git a/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php b/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
index f05b826d64..46ee8c6a14 100644
--- a/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
@@ -74,7 +74,7 @@ public function getIntersect($dp = 0)
      * @param float[] $xValues The set of X-values for this regression
      * @param bool $const
      */
-    private function powerRegression($yValues, $xValues, $const): void
+    private function powerRegression(array $yValues, array $xValues, bool $const): void
     {
         $adjustedYValues = array_map(
             function ($value) {
@@ -104,7 +104,7 @@ public function __construct($yValues, $xValues = [], $const = true)
         parent::__construct($yValues, $xValues);
 
         if (!$this->error) {
-            $this->powerRegression($yValues, $xValues, $const);
+            $this->powerRegression($yValues, $xValues, (bool) $const);
         }
     }
 }
diff --git a/src/PhpSpreadsheet/Shared/Trend/Trend.php b/src/PhpSpreadsheet/Shared/Trend/Trend.php
index 1b7b390107..d0a117cbde 100644
--- a/src/PhpSpreadsheet/Shared/Trend/Trend.php
+++ b/src/PhpSpreadsheet/Shared/Trend/Trend.php
@@ -55,10 +55,9 @@ public static function calculate($trendType = self::TREND_BEST_FIT, $yValues = [
         $nX = count($xValues);
 
         //    Define X Values if necessary
-        if ($nX == 0) {
+        if ($nX === 0) {
             $xValues = range(1, $nY);
-            $nX = $nY;
-        } elseif ($nY != $nX) {
+        } elseif ($nY !== $nX) {
             //    Ensure both arrays of points are the same size
             trigger_error('Trend(): Number of elements in coordinate arrays do not match.', E_USER_ERROR);
         }
@@ -84,7 +83,7 @@ public static function calculate($trendType = self::TREND_BEST_FIT, $yValues = [
             case self::TREND_POLYNOMIAL_6:
                 if (!isset(self::$trendCache[$key])) {
                     $order = substr($trendType, -1);
-                    self::$trendCache[$key] = new PolynomialBestFit($order, $yValues, $xValues, $const);
+                    self::$trendCache[$key] = new PolynomialBestFit($order, $yValues, $xValues);
                 }
 
                 return self::$trendCache[$key];
@@ -100,7 +99,7 @@ public static function calculate($trendType = self::TREND_BEST_FIT, $yValues = [
                 if ($trendType != self::TREND_BEST_FIT_NO_POLY) {
                     foreach (self::$trendTypePolynomialOrders as $trendMethod) {
                         $order = substr($trendMethod, -1);
-                        $bestFit[$trendMethod] = new PolynomialBestFit($order, $yValues, $xValues, $const);
+                        $bestFit[$trendMethod] = new PolynomialBestFit($order, $yValues, $xValues);
                         if ($bestFit[$trendMethod]->getError()) {
                             unset($bestFit[$trendMethod]);
                         } else {

From 18ccc7c19db4ad495cb619980281cb3962b88686 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sat, 6 Mar 2021 18:02:49 +0100
Subject: [PATCH 10/18] Some minor refactoring

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php | 37 ++++++++++++++-------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index 3a1f0b1a1f..6d6f62838a 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -362,7 +362,7 @@ protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY,
         }
 
         $this->SSResiduals = $SSres;
-        $this->DFResiduals = $this->valueCount - 1 - $const;
+        $this->DFResiduals = $this->valueCount - 1 - ($const === true ? 1 : 0);
 
         if ($this->DFResiduals == 0.0) {
             $this->stdevOfResiduals = 0.0;
@@ -395,6 +395,18 @@ protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY,
         }
     }
 
+    private function sumSquares(array $values)
+    {
+        return array_sum(
+            array_map(
+                function ($value) {
+                    return $value ** 2;
+                },
+                $values
+            )
+        );
+    }
+
     /**
      * @param float[] $yValues
      * @param float[] $xValues
@@ -402,19 +414,20 @@ protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY,
     protected function leastSquareFit(array $yValues, array $xValues, bool $const): void
     {
         // calculate sums
-        $x_sum = array_sum($xValues);
-        $y_sum = array_sum($yValues);
-        $meanX = $x_sum / $this->valueCount;
-        $meanY = $y_sum / $this->valueCount;
-        $mBase = $mDivisor = $xx_sum = $xy_sum = $yy_sum = 0.0;
+        $sumValuesX = array_sum($xValues);
+        $sumValuesY = array_sum($yValues);
+        $meanValueX = $sumValuesX / $this->valueCount;
+        $meanValueY = $sumValuesY / $this->valueCount;
+        $sumSquaresX = $this->sumSquares($xValues);
+        $sumSquaresY = $this->sumSquares($yValues);
+        $mBase = $mDivisor = 0.0;
+        $xy_sum = 0.0;
         for ($i = 0; $i < $this->valueCount; ++$i) {
             $xy_sum += $xValues[$i] * $yValues[$i];
-            $xx_sum += $xValues[$i] * $xValues[$i];
-            $yy_sum += $yValues[$i] * $yValues[$i];
 
             if ($const === true) {
-                $mBase += ($xValues[$i] - $meanX) * ($yValues[$i] - $meanY);
-                $mDivisor += ($xValues[$i] - $meanX) * ($xValues[$i] - $meanX);
+                $mBase += ($xValues[$i] - $meanValueX) * ($yValues[$i] - $meanValueY);
+                $mDivisor += ($xValues[$i] - $meanValueX) * ($xValues[$i] - $meanValueX);
             } else {
                 $mBase += $xValues[$i] * $yValues[$i];
                 $mDivisor += $xValues[$i] * $xValues[$i];
@@ -425,9 +438,9 @@ protected function leastSquareFit(array $yValues, array $xValues, bool $const):
         $this->slope = $mBase / $mDivisor;
 
         // calculate intersect
-        $this->intersect = ($const === true) ? $meanY - ($this->slope * $meanX) : 0.0;
+        $this->intersect = ($const === true) ? $meanValueY - ($this->slope * $meanValueX) : 0.0;
 
-        $this->calculateGoodnessOfFit($x_sum, $y_sum, $xx_sum, $yy_sum, $xy_sum, $meanX, $meanY, $const);
+        $this->calculateGoodnessOfFit($sumValuesX, $sumValuesY, $sumSquaresX, $sumSquaresY, $xy_sum, $meanValueX, $meanValueY, $const);
     }
 
     /**

From 06f72267ef70fb081a392500f12b7b3259b3fe58 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sat, 6 Mar 2021 19:06:10 +0100
Subject: [PATCH 11/18] More unit tests

---
 tests/data/Calculation/Statistical/LINEST.php |  7 +++++++
 tests/data/Calculation/Statistical/LOGEST.php | 16 ++++++++++++++--
 tests/data/Shared/Trend/LinearBestFit.php     |  8 ++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/tests/data/Calculation/Statistical/LINEST.php b/tests/data/Calculation/Statistical/LINEST.php
index ff1913bc56..ee5fdb0bde 100644
--- a/tests/data/Calculation/Statistical/LINEST.php
+++ b/tests/data/Calculation/Statistical/LINEST.php
@@ -3,6 +3,13 @@
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 
 return [
+    [
+        [1.0, 0.0],
+        [1, 2, 3, 4, 5],
+        [1, 2, 3, 4, 5],
+        false,
+        false,
+    ],
     [
         [2.310344827586207, 0.0],
         [1, 9, 5, 7],
diff --git a/tests/data/Calculation/Statistical/LOGEST.php b/tests/data/Calculation/Statistical/LOGEST.php
index 38a2ff8d75..bba7487b97 100644
--- a/tests/data/Calculation/Statistical/LOGEST.php
+++ b/tests/data/Calculation/Statistical/LOGEST.php
@@ -1,8 +1,20 @@
 <?php
 
-use PhpOffice\PhpSpreadsheet\Calculation\Functions;
-
 return [
+    [
+        [1.000174230092, 1.0],
+        [1, 2, 3, 4, 5],
+        [1, 10, 100, 1000, 10000],
+        false,
+        false,
+    ],
+    [
+        [1.000091183030, 2.127357620703],
+        [1, 2, 3, 4, 5],
+        [1, 10, 100, 1000, 10000],
+        true,
+        false,
+    ],
     [
         [1.463275628116, 495.304770158727],
         [33100, 47300, 69000, 102000, 150000, 220000],
diff --git a/tests/data/Shared/Trend/LinearBestFit.php b/tests/data/Shared/Trend/LinearBestFit.php
index 1997d404bd..b1be2f9a57 100644
--- a/tests/data/Shared/Trend/LinearBestFit.php
+++ b/tests/data/Shared/Trend/LinearBestFit.php
@@ -9,4 +9,12 @@
         [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
         [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
     ],
+    [
+        'slope' => [1.0, 1.0],
+        'intersect' => [-2.0, -2.0],
+        'goodnessOfFit' => [1.0, 1.0],
+        'equation' => 'Y = -2 + 1 * X',
+        [1, 2, 3, 4, 5],
+        [3, 4, 5, 6, 7],
+    ],
 ];

From f94dbf57694e175df4467d1904cd0d503e67764a Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sat, 6 Mar 2021 19:09:18 +0100
Subject: [PATCH 12/18] PHPCS

---
 src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php | 1 -
 src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php      | 1 -
 src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php | 1 -
 3 files changed, 3 deletions(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php b/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
index 570a12ab17..eb8cd746d3 100644
--- a/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/ExponentialBestFit.php
@@ -88,7 +88,6 @@ public function getIntersect($dp = 0)
      *
      * @param float[] $yValues The set of Y-values for this regression
      * @param float[] $xValues The set of X-values for this regression
-     * @param bool $const
      */
     private function exponentialRegression(array $yValues, array $xValues, bool $const): void
     {
diff --git a/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php b/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php
index 2208447181..65d6b4ff44 100644
--- a/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/LinearBestFit.php
@@ -56,7 +56,6 @@ public function getEquation($dp = 0)
      *
      * @param float[] $yValues The set of Y-values for this regression
      * @param float[] $xValues The set of X-values for this regression
-     * @param bool $const
      */
     private function linearRegression(array $yValues, array $xValues, bool $const): void
     {
diff --git a/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php b/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
index e273263447..2366dc636a 100644
--- a/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/LogarithmicBestFit.php
@@ -56,7 +56,6 @@ public function getEquation($dp = 0)
      *
      * @param float[] $yValues The set of Y-values for this regression
      * @param float[] $xValues The set of X-values for this regression
-     * @param bool $const
      */
     private function logarithmicRegression(array $yValues, array $xValues, bool $const): void
     {

From 3b92899a28c3b48550e459c99c337e2c10290e06 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sat, 6 Mar 2021 19:19:10 +0100
Subject: [PATCH 13/18] PHPCS

---
 src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php b/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
index 46ee8c6a14..cafd01158e 100644
--- a/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/PowerBestFit.php
@@ -72,7 +72,6 @@ public function getIntersect($dp = 0)
      *
      * @param float[] $yValues The set of Y-values for this regression
      * @param float[] $xValues The set of X-values for this regression
-     * @param bool $const
      */
     private function powerRegression(array $yValues, array $xValues, bool $const): void
     {

From 73d400919e9db0e051eead835e91fcbd36e287db Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sat, 6 Mar 2021 23:04:38 +0100
Subject: [PATCH 14/18] Minor typing improvements

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php | 7 -------
 src/PhpSpreadsheet/Shared/Trend/Trend.php   | 2 +-
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index 6d6f62838a..693bf2d8f4 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -39,13 +39,6 @@ class BestFit
      */
     protected $yValues = [];
 
-    /**
-     * Flag indicating whether values should be adjusted to Y=0.
-     *
-     * @var bool
-     */
-    protected $adjustToZero = false;
-
     /**
      * Y-value series of best-fit values.
      *
diff --git a/src/PhpSpreadsheet/Shared/Trend/Trend.php b/src/PhpSpreadsheet/Shared/Trend/Trend.php
index d0a117cbde..fc8e9a2cc0 100644
--- a/src/PhpSpreadsheet/Shared/Trend/Trend.php
+++ b/src/PhpSpreadsheet/Shared/Trend/Trend.php
@@ -96,7 +96,7 @@ public static function calculate($trendType = self::TREND_BEST_FIT, $yValues = [
                     $bestFit[$trendMethod] = new $className($yValues, $xValues, $const);
                     $bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
                 }
-                if ($trendType != self::TREND_BEST_FIT_NO_POLY) {
+                if ($trendType !== self::TREND_BEST_FIT_NO_POLY) {
                     foreach (self::$trendTypePolynomialOrders as $trendMethod) {
                         $order = substr($trendMethod, -1);
                         $bestFit[$trendMethod] = new PolynomialBestFit($order, $yValues, $xValues);

From 6fb8151b6671e298cf7bfc7b347aec47a19d42b9 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sun, 7 Mar 2021 15:39:17 +0100
Subject: [PATCH 15/18] Improvements to BestFit

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php | 101 +++++++-------------
 1 file changed, 34 insertions(+), 67 deletions(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index 693bf2d8f4..e9869cdd26 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -2,7 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheet\Shared\Trend;
 
-class BestFit
+abstract class BestFit
 {
     /**
      * Indicator flag for a calculation error.
@@ -89,24 +89,18 @@ public function getBestFitType()
      *
      * @param float $xValue X-Value
      *
-     * @return bool Y-Value
+     * @return float Y-Value
      */
-    public function getValueOfYForX($xValue)
-    {
-        return false;
-    }
+    abstract public function getValueOfYForX($xValue);
 
     /**
      * Return the X-Value for a specified value of Y.
      *
      * @param float $yValue Y-Value
      *
-     * @return bool X-Value
+     * @return float X-Value
      */
-    public function getValueOfXForY($yValue)
-    {
-        return false;
-    }
+    abstract public function getValueOfXForY($yValue);
 
     /**
      * Return the original set of X-Values.
@@ -123,12 +117,9 @@ public function getXValues()
      *
      * @param int $dp Number of places of decimal precision to display
      *
-     * @return bool
+     * @return string
      */
-    public function getEquation($dp = 0)
-    {
-        return false;
-    }
+    abstract public function getEquation($dp = 0);
 
     /**
      * Return the Slope of the line.
@@ -271,16 +262,10 @@ public function getSSResiduals($dp = 0)
     }
 
     /**
-     * @param int $dp Number of places of decimal precision to return
-     *
-     * @return float
+     * @return int
      */
-    public function getDFResiduals($dp = 0)
+    public function getDFResiduals()
     {
-        if ($dp != 0) {
-            return round($this->DFResiduals, $dp);
-        }
-
         return $this->DFResiduals;
     }
 
@@ -336,55 +321,37 @@ public function getYBestFitValues()
 
     protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY, $meanX, $meanY, $const): void
     {
-        $SSres = $SScov = $SScor = $SStot = $SSsex = 0.0;
+        $SSresiduals = $SScovariance = $SScorrelation = $SStot = $SSsex = 0.0;
         foreach ($this->xValues as $xKey => $xValue) {
             $bestFitY = $this->yBestFitValues[$xKey] = $this->getValueOfYForX($xValue);
 
-            $SSres += ($this->yValues[$xKey] - $bestFitY) * ($this->yValues[$xKey] - $bestFitY);
-            if ($const === true) {
-                $SStot += ($this->yValues[$xKey] - $meanY) * ($this->yValues[$xKey] - $meanY);
-            } else {
-                $SStot += $this->yValues[$xKey] * $this->yValues[$xKey];
-            }
-            $SScov += ($this->xValues[$xKey] - $meanX) * ($this->yValues[$xKey] - $meanY);
-            if ($const === true) {
-                $SSsex += ($this->xValues[$xKey] - $meanX) * ($this->xValues[$xKey] - $meanX);
-            } else {
-                $SSsex += $this->xValues[$xKey] * $this->xValues[$xKey];
-            }
+            $SSresiduals += ($this->yValues[$xKey] - $bestFitY) * ($this->yValues[$xKey] - $bestFitY);
+            $SStot += ($const === true)
+                ? ($this->yValues[$xKey] - $meanY) * ($this->yValues[$xKey] - $meanY)
+                : $this->yValues[$xKey] * $this->yValues[$xKey];
+            $SScovariance += ($this->xValues[$xKey] - $meanX) * ($this->yValues[$xKey] - $meanY);
+            $SSsex += ($const === true)
+                ? ($this->xValues[$xKey] - $meanX) * ($this->xValues[$xKey] - $meanX)
+                : $this->xValues[$xKey] * $this->xValues[$xKey];
         }
 
-        $this->SSResiduals = $SSres;
+        $this->SSResiduals = $SSresiduals;
         $this->DFResiduals = $this->valueCount - 1 - ($const === true ? 1 : 0);
-
-        if ($this->DFResiduals == 0.0) {
-            $this->stdevOfResiduals = 0.0;
-        } else {
-            $this->stdevOfResiduals = sqrt($SSres / $this->DFResiduals);
-        }
-        if (($SStot == 0.0) || ($SSres == $SStot)) {
-            $this->goodnessOfFit = 1;
-        } else {
-            $this->goodnessOfFit = 1 - ($SSres / $SStot);
-        }
+        $this->stdevOfResiduals = ($this->DFResiduals == 0.0) ? 0.0 : sqrt($SSresiduals / $this->DFResiduals);
+        $this->goodnessOfFit = (($SStot == 0.0) || ($SSresiduals == $SStot)) ? 1.0 : 1.0 - ($SSresiduals / $SStot);
 
         $this->SSRegression = $this->goodnessOfFit * $SStot;
-        $this->covariance = $SScov / $this->valueCount;
+        $this->covariance = $SScovariance / $this->valueCount;
         $this->correlation = ($this->valueCount * $sumXY - $sumX * $sumY) / sqrt(($this->valueCount * $sumX2 - $sumX ** 2) * ($this->valueCount * $sumY2 - $sumY ** 2));
         $this->slopeSE = $this->stdevOfResiduals / sqrt($SSsex);
         $this->intersectSE = $this->stdevOfResiduals * sqrt(1 / ($this->valueCount - ($sumX * $sumX) / $sumX2));
+
         if ($this->SSResiduals != 0.0) {
-            if ($this->DFResiduals == 0.0) {
-                $this->f = 0.0;
-            } else {
-                $this->f = $this->SSRegression / ($this->SSResiduals / $this->DFResiduals);
-            }
+            $this->f = ($this->DFResiduals == 0.0)
+                ? 0.0
+                : $this->SSRegression / ($this->SSResiduals / $this->DFResiduals);
         } else {
-            if ($this->DFResiduals == 0.0) {
-                $this->f = 0.0;
-            } else {
-                $this->f = $this->SSRegression / $this->DFResiduals;
-            }
+            $this->f = ($this->DFResiduals == 0.0) ? 0.0 : $this->SSRegression / $this->DFResiduals;
         }
     }
 
@@ -413,18 +380,18 @@ protected function leastSquareFit(array $yValues, array $xValues, bool $const):
         $meanValueY = $sumValuesY / $this->valueCount;
         $sumSquaresX = $this->sumSquares($xValues);
         $sumSquaresY = $this->sumSquares($yValues);
+
         $mBase = $mDivisor = 0.0;
         $xy_sum = 0.0;
         for ($i = 0; $i < $this->valueCount; ++$i) {
             $xy_sum += $xValues[$i] * $yValues[$i];
 
-            if ($const === true) {
-                $mBase += ($xValues[$i] - $meanValueX) * ($yValues[$i] - $meanValueY);
-                $mDivisor += ($xValues[$i] - $meanValueX) * ($xValues[$i] - $meanValueX);
-            } else {
-                $mBase += $xValues[$i] * $yValues[$i];
-                $mDivisor += $xValues[$i] * $xValues[$i];
-            }
+            $mBase += ($const === true)
+                ? ($xValues[$i] - $meanValueX) * ($yValues[$i] - $meanValueY)
+                : $xValues[$i] * $yValues[$i];
+            $mDivisor += ($const === true)
+                ? ($xValues[$i] - $meanValueX) * ($xValues[$i] - $meanValueX)
+                : $xValues[$i] * $xValues[$i];
         }
 
         // calculate slope

From 37bca855ee1ffeb3662a571db92fa3243d15ca81 Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sun, 7 Mar 2021 15:45:08 +0100
Subject: [PATCH 16/18] Resolve merge conflicts

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index a9fc8e4855..e9869cdd26 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -367,18 +367,6 @@ function ($value) {
         );
     }
 
-    private function sumSquares(array $values)
-    {
-        return array_sum(
-            array_map(
-                function ($value) {
-                    return $value ** 2;
-                },
-                $values
-            )
-        );
-    }
-
     /**
      * @param float[] $yValues
      * @param float[] $xValues

From 6d613cd43cd08824b431f8d657fa6e5afeaa82bf Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sun, 7 Mar 2021 16:22:54 +0100
Subject: [PATCH 17/18] Some refactoring of BestFit class

---
 src/PhpSpreadsheet/Shared/Trend/BestFit.php   | 84 +++++++++++--------
 .../Shared/Trend/PolynomialBestFit.php        |  2 +-
 .../Shared/Trend/LogarithmicBestFitTest.php   | 49 +++++++++++
 .../data/Shared/Trend/LogarithmicBestFit.php  | 12 +++
 4 files changed, 111 insertions(+), 36 deletions(-)
 create mode 100644 tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php
 create mode 100644 tests/data/Shared/Trend/LogarithmicBestFit.php

diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index e9869cdd26..4efb109d0b 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -319,52 +319,68 @@ public function getYBestFitValues()
         return $this->yBestFitValues;
     }
 
-    protected function calculateGoodnessOfFit($sumX, $sumY, $sumX2, $sumY2, $sumXY, $meanX, $meanY, $const): void
+    private function sumSquares(array $values): float
     {
-        $SSresiduals = $SScovariance = $SScorrelation = $SStot = $SSsex = 0.0;
-        foreach ($this->xValues as $xKey => $xValue) {
-            $bestFitY = $this->yBestFitValues[$xKey] = $this->getValueOfYForX($xValue);
+        return array_sum(
+            array_map(
+                function ($value) {
+                    return $value ** 2;
+                },
+                $values
+            )
+        );
+    }
 
-            $SSresiduals += ($this->yValues[$xKey] - $bestFitY) * ($this->yValues[$xKey] - $bestFitY);
-            $SStot += ($const === true)
-                ? ($this->yValues[$xKey] - $meanY) * ($this->yValues[$xKey] - $meanY)
-                : $this->yValues[$xKey] * $this->yValues[$xKey];
-            $SScovariance += ($this->xValues[$xKey] - $meanX) * ($this->yValues[$xKey] - $meanY);
-            $SSsex += ($const === true)
-                ? ($this->xValues[$xKey] - $meanX) * ($this->xValues[$xKey] - $meanX)
-                : $this->xValues[$xKey] * $this->xValues[$xKey];
-        }
+    /**
+     * @param $sumXY
+     * @param $sumValuesX
+     * @param $sumValuesY
+     */
+    protected function calculateGoodnessOfFit(float $SStot, $sumXY, $sumValuesX, $sumValuesY, float $SSsex): void
+    {
+        $sumSquaresX = $this->sumSquares($this->xValues);
+        $sumSquaresY = $this->sumSquares($this->yValues);
 
-        $this->SSResiduals = $SSresiduals;
-        $this->DFResiduals = $this->valueCount - 1 - ($const === true ? 1 : 0);
-        $this->stdevOfResiduals = ($this->DFResiduals == 0.0) ? 0.0 : sqrt($SSresiduals / $this->DFResiduals);
-        $this->goodnessOfFit = (($SStot == 0.0) || ($SSresiduals == $SStot)) ? 1.0 : 1.0 - ($SSresiduals / $SStot);
+        $this->stdevOfResiduals = ($this->DFResiduals == 0.0) ? 0.0 : sqrt($this->SSResiduals / $this->DFResiduals);
+        $this->goodnessOfFit = (($SStot == 0.0) || ($this->SSResiduals == $SStot))
+            ? 1.0
+            : 1.0 - ($this->SSResiduals / $SStot);
 
         $this->SSRegression = $this->goodnessOfFit * $SStot;
-        $this->covariance = $SScovariance / $this->valueCount;
-        $this->correlation = ($this->valueCount * $sumXY - $sumX * $sumY) / sqrt(($this->valueCount * $sumX2 - $sumX ** 2) * ($this->valueCount * $sumY2 - $sumY ** 2));
+        $this->correlation = ($this->valueCount * $sumXY - $sumValuesX * $sumValuesY) /
+            sqrt(($this->valueCount * $sumSquaresX - $sumValuesX ** 2) * ($this->valueCount * $sumSquaresY - $sumValuesY ** 2));
         $this->slopeSE = $this->stdevOfResiduals / sqrt($SSsex);
-        $this->intersectSE = $this->stdevOfResiduals * sqrt(1 / ($this->valueCount - ($sumX * $sumX) / $sumX2));
+        $this->intersectSE = $this->stdevOfResiduals *
+            sqrt(1 / ($this->valueCount - ($sumValuesX * $sumValuesX) / $sumSquaresX));
 
         if ($this->SSResiduals != 0.0) {
-            $this->f = ($this->DFResiduals == 0.0)
-                ? 0.0
-                : $this->SSRegression / ($this->SSResiduals / $this->DFResiduals);
+            $this->f = ($this->DFResiduals == 0.0) ? 0.0 : $this->SSRegression / ($this->SSResiduals / $this->DFResiduals);
         } else {
             $this->f = ($this->DFResiduals == 0.0) ? 0.0 : $this->SSRegression / $this->DFResiduals;
         }
     }
 
-    private function sumSquares(array $values)
+    protected function calculateResiduals($sumValuesX, $sumValuesY, $sumXY, $meanValueX, $meanYmeanValueY, $const): void
     {
-        return array_sum(
-            array_map(
-                function ($value) {
-                    return $value ** 2;
-                },
-                $values
-            )
-        );
+        $SSresiduals = $SScovariance = $SStot = $SSsex = 0.0;
+        foreach ($this->xValues as $xKey => $xValue) {
+            $bestFitY = $this->yBestFitValues[$xKey] = $this->getValueOfYForX($xValue);
+
+            $SSresiduals += ($this->yValues[$xKey] - $bestFitY) * ($this->yValues[$xKey] - $bestFitY);
+            $SStot += ($const === true)
+                ? ($this->yValues[$xKey] - $meanYmeanValueY) * ($this->yValues[$xKey] - $meanYmeanValueY)
+                : $this->yValues[$xKey] * $this->yValues[$xKey];
+            $SScovariance += ($this->xValues[$xKey] - $meanValueX) * ($this->yValues[$xKey] - $meanYmeanValueY);
+            $SSsex += ($const === true)
+                ? ($this->xValues[$xKey] - $meanValueX) * ($this->xValues[$xKey] - $meanValueX)
+                : $this->xValues[$xKey] * $this->xValues[$xKey];
+        }
+
+        $this->DFResiduals = $this->valueCount - 1 - ($const === true ? 1 : 0);
+        $this->SSResiduals = $SSresiduals;
+        $this->covariance = $SScovariance / $this->valueCount;
+
+        $this->calculateGoodnessOfFit($SStot, $sumXY, $sumValuesX, $sumValuesY, $SSsex);
     }
 
     /**
@@ -378,8 +394,6 @@ protected function leastSquareFit(array $yValues, array $xValues, bool $const):
         $sumValuesY = array_sum($yValues);
         $meanValueX = $sumValuesX / $this->valueCount;
         $meanValueY = $sumValuesY / $this->valueCount;
-        $sumSquaresX = $this->sumSquares($xValues);
-        $sumSquaresY = $this->sumSquares($yValues);
 
         $mBase = $mDivisor = 0.0;
         $xy_sum = 0.0;
@@ -400,7 +414,7 @@ protected function leastSquareFit(array $yValues, array $xValues, bool $const):
         // calculate intersect
         $this->intersect = ($const === true) ? $meanValueY - ($this->slope * $meanValueX) : 0.0;
 
-        $this->calculateGoodnessOfFit($sumValuesX, $sumValuesY, $sumSquaresX, $sumSquaresY, $xy_sum, $meanValueX, $meanValueY, $const);
+        $this->calculateResiduals($sumValuesX, $sumValuesY, $xy_sum, $meanValueX, $meanValueY, $const);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php b/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
index 1d34e81c19..feb382ab91 100644
--- a/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
@@ -166,7 +166,7 @@ private function polynomialRegression($order, $yValues, $xValues): void
         $this->intersect = array_shift($coefficients);
         $this->slope = $coefficients;
 
-        $this->calculateGoodnessOfFit($x_sum, $y_sum, $xx_sum, $yy_sum, $xy_sum, 0, 0, 0);
+        $this->calculateResiduals($x_sum, $y_sum, $xx_sum, $yy_sum, $xy_sum, 0, 0, 0);
         foreach ($this->xValues as $xKey => $xValue) {
             $this->yBestFitValues[$xKey] = $this->getValueOfYForX($xValue);
         }
diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php
new file mode 100644
index 0000000000..eef5ffc961
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Shared\Trend;
+
+use PhpOffice\PhpSpreadsheet\Shared\Trend\LogarithmicBestFit;
+use PHPUnit\Framework\TestCase;
+
+class LogarithmicBestFitTest extends TestCase
+{
+    /**
+     * @dataProvider providerLogarithmicBestFit
+     *
+     * @param mixed $expectedSlope
+     * @param mixed $expectedIntersect
+     * @param mixed $expectedGoodnessOfFit
+     * @param mixed $yValues
+     * @param mixed $xValues
+     * @param mixed $expectedEquation
+     */
+    public function testLogBestFit(
+        $expectedSlope,
+        $expectedIntersect,
+        $expectedGoodnessOfFit,
+        $expectedEquation,
+        $yValues,
+        $xValues
+    ): void {
+        $bestFit = new LogarithmicBestFit($yValues, $xValues);
+        $slope = $bestFit->getSlope(1);
+        self::assertEquals($expectedSlope[0], $slope);
+        $slope = $bestFit->getSlope();
+        self::assertEquals($expectedSlope[1], $slope);
+        $intersect = $bestFit->getIntersect(1);
+        self::assertEquals($expectedIntersect[0], $intersect);
+        $intersect = $bestFit->getIntersect();
+        self::assertEquals($expectedIntersect[1], $intersect);
+
+        $equation = $bestFit->getEquation(2);
+        self::assertEquals($expectedEquation, $equation);
+
+        self::assertSame($expectedGoodnessOfFit[0], $bestFit->getGoodnessOfFit(6));
+        self::assertSame($expectedGoodnessOfFit[1], $bestFit->getGoodnessOfFit());
+    }
+
+    public function providerLogarithmicBestFit()
+    {
+        return require 'tests/data/Shared/Trend/LogarithmicBestFit.php';
+    }
+}
diff --git a/tests/data/Shared/Trend/LogarithmicBestFit.php b/tests/data/Shared/Trend/LogarithmicBestFit.php
new file mode 100644
index 0000000000..98d91004ad
--- /dev/null
+++ b/tests/data/Shared/Trend/LogarithmicBestFit.php
@@ -0,0 +1,12 @@
+<?php
+
+return [
+    [
+        'slope' => [-4.9, -4.918384677001153],
+        'intersect' => [15.1, 15.081824008436346],
+        'goodnessOfFit' => [0.949372, 0.949372],
+        'equation' => 'Y = 14.08 + -1.11 * X',
+        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
+        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
+    ],
+];

From 69c77d980f2bae2cefc7c8c71d52a6a905718b2e Mon Sep 17 00:00:00 2001
From: MarkBaker <mark@lange.demon.co.uk>
Date: Sun, 7 Mar 2021 16:24:26 +0100
Subject: [PATCH 18/18] Some refactoring of BestFit class

---
 .../Shared/Trend/LogarithmicBestFitTest.php   | 49 -------------------
 .../data/Shared/Trend/LogarithmicBestFit.php  | 12 -----
 2 files changed, 61 deletions(-)
 delete mode 100644 tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php
 delete mode 100644 tests/data/Shared/Trend/LogarithmicBestFit.php

diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php
deleted file mode 100644
index eef5ffc961..0000000000
--- a/tests/PhpSpreadsheetTests/Shared/Trend/LogarithmicBestFitTest.php
+++ /dev/null
@@ -1,49 +0,0 @@
-<?php
-
-namespace PhpOffice\PhpSpreadsheetTests\Shared\Trend;
-
-use PhpOffice\PhpSpreadsheet\Shared\Trend\LogarithmicBestFit;
-use PHPUnit\Framework\TestCase;
-
-class LogarithmicBestFitTest extends TestCase
-{
-    /**
-     * @dataProvider providerLogarithmicBestFit
-     *
-     * @param mixed $expectedSlope
-     * @param mixed $expectedIntersect
-     * @param mixed $expectedGoodnessOfFit
-     * @param mixed $yValues
-     * @param mixed $xValues
-     * @param mixed $expectedEquation
-     */
-    public function testLogBestFit(
-        $expectedSlope,
-        $expectedIntersect,
-        $expectedGoodnessOfFit,
-        $expectedEquation,
-        $yValues,
-        $xValues
-    ): void {
-        $bestFit = new LogarithmicBestFit($yValues, $xValues);
-        $slope = $bestFit->getSlope(1);
-        self::assertEquals($expectedSlope[0], $slope);
-        $slope = $bestFit->getSlope();
-        self::assertEquals($expectedSlope[1], $slope);
-        $intersect = $bestFit->getIntersect(1);
-        self::assertEquals($expectedIntersect[0], $intersect);
-        $intersect = $bestFit->getIntersect();
-        self::assertEquals($expectedIntersect[1], $intersect);
-
-        $equation = $bestFit->getEquation(2);
-        self::assertEquals($expectedEquation, $equation);
-
-        self::assertSame($expectedGoodnessOfFit[0], $bestFit->getGoodnessOfFit(6));
-        self::assertSame($expectedGoodnessOfFit[1], $bestFit->getGoodnessOfFit());
-    }
-
-    public function providerLogarithmicBestFit()
-    {
-        return require 'tests/data/Shared/Trend/LogarithmicBestFit.php';
-    }
-}
diff --git a/tests/data/Shared/Trend/LogarithmicBestFit.php b/tests/data/Shared/Trend/LogarithmicBestFit.php
deleted file mode 100644
index 98d91004ad..0000000000
--- a/tests/data/Shared/Trend/LogarithmicBestFit.php
+++ /dev/null
@@ -1,12 +0,0 @@
-<?php
-
-return [
-    [
-        'slope' => [-4.9, -4.918384677001153],
-        'intersect' => [15.1, 15.081824008436346],
-        'goodnessOfFit' => [0.949372, 0.949372],
-        'equation' => 'Y = 14.08 + -1.11 * X',
-        [3, 10, 3, 6, 8, 12, 1, 4, 9, 14],
-        [8, 2, 11, 6, 5, 4, 12, 9, 6, 1],
-    ],
-];