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lib/PhpSpreadsheet/Calculation/Engineering/ErfC.php

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+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\Engineering;
+
+use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
+
+class ErfC
+{
+    use ArrayEnabled;
+
+    /**
+     * ERFC.
+     *
+     *    Returns the complementary ERF function integrated between x and infinity
+     *
+     *    Note: In Excel 2007 or earlier, if you input a negative value for the lower bound argument,
+     *        the function would return a #NUM! error. However, in Excel 2010, the function algorithm was
+     *        improved, so that it can now calculate the function for both positive and negative x values.
+     *            PhpSpreadsheet follows Excel 2010 behaviour, and accepts nagative arguments.
+     *
+     *    Excel Function:
+     *        ERFC(x)
+     *
+     * @param mixed $value The float lower bound for integrating ERFC
+     *                      Or can be an array of values
+     *
+     * @return array|float|string If an array of numbers is passed as an argument, then the returned result will also be an array
+     *            with the same dimensions
+     */
+    public static function ERFC(mixed $value)
+    {
+        if (is_array($value)) {
+            return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $value);
+        }
+
+        if (is_numeric($value)) {
+            return self::erfcValue($value);
+        }
+
+        return ExcelError::VALUE();
+    }
+
+    private const ONE_SQRT_PI = 0.564189583547756287;
+
+    /**
+     * Method to calculate the erfc value.
+     */
+    private static function erfcValue(float|int|string $value): float|int
+    {
+        $value = (float) $value;
+        if (abs($value) < 2.2) {
+            return 1 - Erf::erfValue($value);
+        }
+        if ($value < 0) {
+            return 2 - self::erfcValue(-$value);
+        }
+        $a = $n = 1;
+        $b = $c = $value;
+        $d = ($value * $value) + 0.5;
+        $q2 = $b / $d;
+        do {
+            $t = $a * $n + $b * $value;
+            $a = $b;
+            $b = $t;
+            $t = $c * $n + $d * $value;
+            $c = $d;
+            $d = $t;
+            $n += 0.5;
+            $q1 = $q2;
+            $q2 = $b / $d;
+        } while ((abs($q1 - $q2) / $q2) > Functions::PRECISION);
+
+        return self::ONE_SQRT_PI * exp(-$value * $value) * $q2;
+    }
+}