init

lib/PhpSpreadsheet/Calculation/Statistical/Distributions/Weibull.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;
+
+use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception;
+use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
+
+class Weibull
+{
+    use ArrayEnabled;
+
+    /**
+     * WEIBULL.
+     *
+     * Returns the Weibull distribution. Use this distribution in reliability
+     * analysis, such as calculating a device's mean time to failure.
+     *
+     * @param mixed $value Float value for the distribution
+     *                      Or can be an array of values
+     * @param mixed $alpha Float alpha Parameter
+     *                      Or can be an array of values
+     * @param mixed $beta Float beta Parameter
+     *                      Or can be an array of values
+     * @param mixed $cumulative Boolean value indicating if we want the cdf (true) or the pdf (false)
+     *                      Or can be an array of values
+     *
+     * @return array|float|string (string if result is an error)
+     *         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 distribution(mixed $value, mixed $alpha, mixed $beta, mixed $cumulative): array|string|float
+    {
+        if (is_array($value) || is_array($alpha) || is_array($beta) || is_array($cumulative)) {
+            return self::evaluateArrayArguments([self::class, __FUNCTION__], $value, $alpha, $beta, $cumulative);
+        }
+
+        try {
+            $value = DistributionValidations::validateFloat($value);
+            $alpha = DistributionValidations::validateFloat($alpha);
+            $beta = DistributionValidations::validateFloat($beta);
+            $cumulative = DistributionValidations::validateBool($cumulative);
+        } catch (Exception $e) {
+            return $e->getMessage();
+        }
+
+        if (($value < 0) || ($alpha <= 0) || ($beta <= 0)) {
+            return ExcelError::NAN();
+        }
+
+        if ($cumulative) {
+            return 1 - exp(0 - ($value / $beta) ** $alpha);
+        }
+
+        return ($alpha / $beta ** $alpha) * $value ** ($alpha - 1) * exp(0 - ($value / $beta) ** $alpha);
+    }
+}