MediaWiki 1.30.2

[autoinstalls/mediawiki.git] / vendor / wikimedia / running-stat / README.md

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+RunningStat
+===========
+
+RunningStat computes the central tendency, shape, and extrema of a set of
+points online, in constant space. It uses a neat one-pass algorithm for
+calculating variance, described here:
+       <en.wikipedia.org/wiki/Algorithms_for_calculating_variance#On-line_algorithm>
+
+This particular implementation adapts a sample C++ implementation by John D.
+Cook to PHP. See <http://www.johndcook.com/standard_deviation.html> and
+       <http://www.johndcook.com/skewness_kurtosis.html>.
+
+RunningStat instances can be combined. The resultant RunningStat has the same
+state it would have had if it had been used to accumulate each point. This
+property is attractive because it allows separate threads of execution to
+process a stream in parallel. More importantly, individual points can be
+accumulated in stages, without loss of fidelity, at intermediate points in the
+aggregation process. JavaScript profiling samples can be accumulated in the
+user's browser and be combined with measurements from other browsers on the
+profiling data aggregator. Functions that are called multiple times in the
+course of a profiled web request can be accumulated in MediaWiki prior to being
+transmitted to the profiling data aggregator.
+
+Usage
+-----
+Here is how you use it:
+
+<pre lang="php">
+use RunningStat\RunningStat;
+
+$rstat = new RunningStat();
+foreach ( array(
+  49.7168, 74.3804,  7.0115, 96.5769, 34.9458,
+  36.9947, 33.8926, 89.0774, 23.7745, 73.5154,
+  86.1322, 53.2124, 16.2046, 73.5130, 10.4209,
+  42.7299, 49.3330, 47.0215, 34.9950, 18.2914,
+) as $sample ) {
+  $rstat->addObservation( $sample );
+}
+
+
+printf(
+  "n = %d; min = %.2f; max = %.2f; mean = %.2f; variance = %.2f; stddev = %.2f\n",
+  count( $rstat ),
+  $rstat->min,
+  $rstat->max,
+  $rstat->getMean(),
+  $rstat->getVariance(),
+  $rstat->getStdDev()
+);
+// Output:
+// n = 20; min = 7.01; max = 96.58; mean = 47.59; variance = 725.71; stddev = 26.94
+</pre>
+
+License
+-------
+GPL-2.0+