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lib/PhpSpreadsheet/Calculation/Engineering/Erf.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 Erf
+{
+    use ArrayEnabled;
+
+    private const TWO_SQRT_PI = 1.128379167095512574;
+
+    /**
+     * ERF.
+     *
+     * Returns the error function integrated between the lower and upper bound arguments.
+     *
+     *    Note: In Excel 2007 or earlier, if you input a negative value for the upper or lower bound arguments,
+     *            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 ranges.
+     *            PhpSpreadsheet follows Excel 2010 behaviour, and accepts negative arguments.
+     *
+     *    Excel Function:
+     *        ERF(lower[,upper])
+     *
+     * @param mixed $lower Lower bound float for integrating ERF
+     *                      Or can be an array of values
+     * @param mixed $upper Upper bound float for integrating ERF.
+     *                           If omitted, ERF integrates between zero and lower_limit
+     *                      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 ERF(mixed $lower, mixed $upper = null): array|float|string
+    {
+        if (is_array($lower) || is_array($upper)) {
+            return self::evaluateArrayArguments([self::class, __FUNCTION__], $lower, $upper);
+        }
+
+        if (is_numeric($lower)) {
+            if ($upper === null) {
+                return self::erfValue($lower);
+            }
+            if (is_numeric($upper)) {
+                return self::erfValue($upper) - self::erfValue($lower);
+            }
+        }
+
+        return ExcelError::VALUE();
+    }
+
+    /**
+     * ERFPRECISE.
+     *
+     * Returns the error function integrated between the lower and upper bound arguments.
+     *
+     *    Excel Function:
+     *        ERF.PRECISE(limit)
+     *
+     * @param mixed $limit Float bound for integrating ERF, other bound is zero
+     *                      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 ERFPRECISE(mixed $limit)
+    {
+        if (is_array($limit)) {
+            return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $limit);
+        }
+
+        return self::ERF($limit);
+    }
+
+    private static function makeFloat(mixed $value): float
+    {
+        return is_numeric($value) ? ((float) $value) : 0.0;
+    }
+
+    /**
+     * Method to calculate the erf value.
+     */
+    public static function erfValue(float|int|string $value): float
+    {
+        $value = (float) $value;
+        if (abs($value) > 2.2) {
+            return 1 - self::makeFloat(ErfC::ERFC($value));
+        }
+        $sum = $term = $value;
+        $xsqr = ($value * $value);
+        $j = 1;
+        do {
+            $term *= $xsqr / $j;
+            $sum -= $term / (2 * $j + 1);
+            ++$j;
+            $term *= $xsqr / $j;
+            $sum += $term / (2 * $j + 1);
+            ++$j;
+            if ($sum == 0.0) {
+                break;
+            }
+        } while (abs($term / $sum) > Functions::PRECISION);
+
+        return self::TWO_SQRT_PI * $sum;
+    }
+}