Trend function unit tests (#1089)

* Merge branch 'master' of C:\Projects\PHPOffice\PHPSpreadsheet\develop with conflicts.

* More trend function unit tests

* Yet more trend function unit tests

tests/PhpSpreadsheetTests/Calculation/StatisticalTest.php

@@ -253,6 +253,22 @@ class StatisticalTest extends TestCase
         return require 'data/Calculation/Statistical/FORECAST.php';
     }
 
+    /**
+     * @dataProvider providerINTERCEPT
+     *
+     * @param mixed $expectedResult
+     */
+    public function testINTERCEPT($expectedResult, array $xargs, array $yargs)
+    {
+        $result = Statistical::INTERCEPT($xargs, $yargs);
+        self::assertEquals($expectedResult, $result, '', 1E-12);
+    }
+
+    public function providerINTERCEPT()
+    {
+        return require 'data/Calculation/Statistical/INTERCEPT.php';
+    }
+
     /**
      * @dataProvider providerMAXIFS
      *
@@ -284,4 +300,52 @@ class StatisticalTest extends TestCase
     {
         return require 'data/Calculation/Statistical/MINIFS.php';
     }
+
+    /**
+     * @dataProvider providerRSQ
+     *
+     * @param mixed $expectedResult
+     */
+    public function testRSQ($expectedResult, array $xargs, array $yargs)
+    {
+        $result = Statistical::RSQ($xargs, $yargs);
+        self::assertEquals($expectedResult, $result, '', 1E-12);
+    }
+
+    public function providerRSQ()
+    {
+        return require 'data/Calculation/Statistical/RSQ.php';
+    }
+
+    /**
+     * @dataProvider providerSLOPE
+     *
+     * @param mixed $expectedResult
+     */
+    public function testSLOPE($expectedResult, array $xargs, array $yargs)
+    {
+        $result = Statistical::SLOPE($xargs, $yargs);
+        self::assertEquals($expectedResult, $result, '', 1E-12);
+    }
+
+    public function providerSLOPE()
+    {
+        return require 'data/Calculation/Statistical/SLOPE.php';
+    }
+
+    /**
+     * @dataProvider providerSTEYX
+     *
+     * @param mixed $expectedResult
+     */
+    public function testSTEYX($expectedResult, array $xargs, array $yargs)
+    {
+        $result = Statistical::STEYX($xargs, $yargs);
+        self::assertEquals($expectedResult, $result, '', 1E-12);
+    }
+
+    public function providerSTEYX()
+    {
+        return require 'data/Calculation/Statistical/STEYX.php';
+    }
 }

tests/data/Calculation/Statistical/FORECAST.php

@@ -37,4 +37,10 @@ return [
         [-1, -2, -3, -4],
         [10, 20, 30, 40],
     ],
+    [
+        32.666666666667,
+        7,
+        [3, 7, 15, 20, 22, 27],
+        [1, 2, 3, 4, 5, 6],
+    ],
 ];

tests/data/Calculation/Statistical/INTERCEPT.php

@@ -0,0 +1,29 @@
+<?php
+
+return [
+    [
+        25.0,
+        [5, 10, 15, 20],
+        [12, 9, 6, 3],
+    ],
+    [
+        -9.0,
+        [1, 2, 3, 4],
+        [10, 11, 12, 13],
+    ],
+    [
+        0.0,
+        [10, 20, 30],
+        [10, 20, 30],
+    ],
+    [
+        0.048387096774,
+        [2, 3, 9, 1, 8],
+        [6, 5, 11, 7, 5],
+    ],
+    [
+        2.4,
+        [6, 9, 17, 20, 20, 27],
+        [1, 2, 3, 4, 5, 6],
+    ],
+];

tests/data/Calculation/Statistical/RSQ.php

@@ -0,0 +1,14 @@
+<?php
+
+return [
+    [
+        0.057950191571,
+        [2, 3, 9, 1, 8, 7, 5],
+        [6, 5, 11, 7, 5, 4, 4],
+    ],
+    [
+        0.711666290487,
+        [2, 7, 8, 3, 4, 1, 6, 5],
+        [22.9, 33.49, 34.5, 27.61, 19.5, 10.11, 37.90, 31.08],
+    ],
+];

tests/data/Calculation/Statistical/SLOPE.php

@@ -0,0 +1,68 @@
+<?php
+
+use PhpOffice\PhpSpreadsheet\Shared\Date;
+
+return [
+    [
+        0.6,
+        [3, 6, 9, 12],
+        [5, 10, 15, 20],
+    ],
+    [
+        1.0,
+        [1, 2, 3, 4],
+        [10, 11, 12, 13],
+    ],
+    [
+        0.2,
+        [2, 4, 6],
+        [10, 20, 30],
+    ],
+    [
+        4.628571428571,
+        [3, 7, 17, 20, 20, 27],
+        [1, 2, 3, 4, 5, 6],
+    ],
+    [
+        9.472222222222,
+        [
+            Date::stringToExcel('1900-02-01'),
+            Date::stringToExcel('1900-03-01'),
+            Date::stringToExcel('1900-09-01'),
+            Date::stringToExcel('1900-01-01'),
+            Date::stringToExcel('1900-08-01'),
+            Date::stringToExcel('1900-07-01'),
+            Date::stringToExcel('1900-05-01'),
+        ],
+        [
+            6,
+            5,
+            11,
+            7,
+            5,
+            4,
+            4,
+        ]
+    ],
+    [
+        0.305555555556,
+        [
+            Date::stringToExcel('1900-01-02'),
+            Date::stringToExcel('1900-01-03'),
+            Date::stringToExcel('1900-01-09'),
+            Date::stringToExcel('1900-01-01'),
+            Date::stringToExcel('1900-01-08'),
+            Date::stringToExcel('1900-01-07'),
+            Date::stringToExcel('1900-01-05'),
+        ],
+        [
+            6,
+            5,
+            11,
+            7,
+            5,
+            4,
+            4,
+        ]
+    ],
+];

tests/data/Calculation/Statistical/STEYX.php

@@ -0,0 +1,14 @@
+<?php
+
+return [
+    [
+        3.305718950210,
+        [2, 3, 9, 1, 8, 7, 5],
+        [6, 5, 11, 7, 5, 4, 4],
+    ],
+    [
+        1.201186346682,
+        [3, 7.9, 8, 9.2, 12, 10.5, 15, 15.5, 17],
+        [1, 2, 3, 4, 4.5, 5, 6, 7, 8],
+    ],
+];