From c1f9b1f7b1b77776192048005dcc66dcf3df2bfb Mon Sep 17 00:00:00 2001
From: Pierre Schmitz <pierre@archlinux.de>
Date: Sat, 27 Dec 2014 15:41:37 +0100
Subject: Update to MediaWiki 1.24.1

---
 includes/libs/RunningStat.php | 176 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 176 insertions(+)
 create mode 100644 includes/libs/RunningStat.php

(limited to 'includes/libs/RunningStat.php')

diff --git a/includes/libs/RunningStat.php b/includes/libs/RunningStat.php
new file mode 100644
index 00000000..dda5254e
--- /dev/null
+++ b/includes/libs/RunningStat.php
@@ -0,0 +1,176 @@
+<?php
+/**
+ * Compute running mean, variance, and extrema of a stream of numbers.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Profiler
+ */
+
+// Needed due to PHP non-bug <https://bugs.php.net/bug.php?id=49828>.
+define( 'NEGATIVE_INF', -INF );
+
+/**
+ * Represents a running summary of a stream of numbers.
+ *
+ * RunningStat instances are accumulator-like objects that provide a set of
+ * continuously-updated summary statistics for a stream of numbers, without
+ * requiring that each value be stored. The measures it provides are the
+ * arithmetic mean, variance, standard deviation, and extrema (min and max);
+ * together they describe the central tendency and statistical dispersion of a
+ * set of values.
+ *
+ * One RunningStat instance can be merged into another; the resultant
+ * RunningStat has the state it would have had if it had accumulated each
+ * individual point. This allows data to be summarized in parallel and in
+ * stages without loss of fidelity.
+ *
+ * Based on a C++ implementation by John D. Cook:
+ *  <http://www.johndcook.com/standard_deviation.html>
+ *  <http://www.johndcook.com/skewness_kurtosis.html>
+ *
+ * The in-line documentation for this class incorporates content from the
+ * English Wikipedia articles "Variance", "Algorithms for calculating
+ * variance", and "Standard deviation".
+ *
+ * @since 1.23
+ */
+class RunningStat implements Countable {
+
+	/** @var int Number of samples. **/
+	public $n = 0;
+
+	/** @var float The first moment (or mean, or expected value). **/
+	public $m1 = 0.0;
+
+	/** @var float The second central moment (or variance). **/
+	public $m2 = 0.0;
+
+	/** @var float The least value in the the set. **/
+	public $min = INF;
+
+	/** @var float The most value in the set. **/
+	public $max = NEGATIVE_INF;
+
+	/**
+	 * Count the number of accumulated values.
+	 * @return int Number of values
+	 */
+	public function count() {
+		return $this->n;
+	}
+
+	/**
+	 * Add a number to the data set.
+	 * @param int|float $x Value to add
+	 */
+	public function push( $x ) {
+		$x = (float) $x;
+
+		$this->min = min( $this->min, $x );
+		$this->max = max( $this->max, $x );
+
+		$n1 = $this->n;
+		$this->n += 1;
+		$delta = $x - $this->m1;
+		$delta_n = $delta / $this->n;
+		$this->m1 += $delta_n;
+		$this->m2 += $delta * $delta_n * $n1;
+	}
+
+	/**
+	 * Get the mean, or expected value.
+	 *
+	 * The arithmetic mean is the sum of all measurements divided by the number
+	 * of observations in the data set.
+	 *
+	 * @return float Mean
+	 */
+	public function getMean() {
+		return $this->m1;
+	}
+
+	/**
+	 * Get the estimated variance.
+	 *
+	 * Variance measures how far a set of numbers is spread out. A small
+	 * variance indicates that the data points tend to be very close to the
+	 * mean (and hence to each other), while a high variance indicates that the
+	 * data points are very spread out from the mean and from each other.
+	 *
+	 * @return float Estimated variance
+	 */
+	public function getVariance() {
+		if ( $this->n === 0 ) {
+			// The variance of the empty set is undefined.
+			return NAN;
+		} elseif ( $this->n === 1 ) {
+			return 0.0;
+		} else {
+			return $this->m2 / ( $this->n - 1.0 );
+		}
+	}
+
+	/**
+	 * Get the estimated stanard deviation.
+	 *
+	 * The standard deviation of a statistical population is the square root of
+	 * its variance. It shows shows how much variation from the mean exists. In
+	 * addition to expressing the variability of a population, the standard
+	 * deviation is commonly used to measure confidence in statistical conclusions.
+	 *
+	 * @return float Estimated standard deviation
+	 */
+	public function getStdDev() {
+		return sqrt( $this->getVariance() );
+	}
+
+	/**
+	 * Merge another RunningStat instance into this instance.
+	 *
+	 * This instance then has the state it would have had if all the data had
+	 * been accumulated by it alone.
+	 *
+	 * @param RunningStat RunningStat instance to merge into this one
+	 */
+	public function merge( RunningStat $other ) {
+		// If the other RunningStat is empty, there's nothing to do.
+		if ( $other->n === 0 ) {
+			return;
+		}
+
+		// If this RunningStat is empty, copy values from other RunningStat.
+		if ( $this->n === 0 ) {
+			$this->n = $other->n;
+			$this->m1 = $other->m1;
+			$this->m2 = $other->m2;
+			$this->min = $other->min;
+			$this->max = $other->max;
+			return;
+		}
+
+		$n = $this->n + $other->n;
+		$delta = $other->m1 - $this->m1;
+		$delta2 = $delta * $delta;
+
+		$this->m1 = ( ( $this->n * $this->m1 ) + ( $other->n * $other->m1 ) ) / $n;
+		$this->m2 = $this->m2 + $other->m2 + ( $delta2 * $this->n * $other->n / $n );
+		$this->min = min( $this->min, $other->min );
+		$this->max = max( $this->max, $other->max );
+		$this->n = $n;
+	}
+}
-- 
cgit v1.2.3-54-g00ecf