RunningStatTest.php

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<?php
class RunningStatTest extends MediaWikiTestCase {

    public $points = 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,
    );

    public function testRunningStatAccuracy() {
        $rstat = new RunningStat();
        foreach( $this->points as $point ) {
            $rstat->push( $point );
        }

        $mean = array_sum( $this->points ) / count( $this->points );
        $variance = array_sum( array_map( function ( $x ) use ( $mean ) {
            return pow( $mean - $x, 2 );
        }, $this->points ) ) / ( count( $rstat ) - 1 );
        $stddev = sqrt( $variance );

        $this->assertEquals( count( $rstat ), count( $this->points ) );
        $this->assertEquals( $rstat->min, min( $this->points ) );
        $this->assertEquals( $rstat->max, max( $this->points ) );
        $this->assertEquals( $rstat->getMean(), $mean );
        $this->assertEquals( $rstat->getVariance(), $variance );
        $this->assertEquals( $rstat->getStdDev(), $stddev );
    }

    public function testRunningStatMerge() {
        $expected = new RunningStat();

        foreach( $this->points as $point ) {
            $expected->push( $point );
        }

        // Split the data into two sets
        $sets = array_chunk( $this->points, floor( count( $this->points ) / 2 ) );

        // Accumulate the first half into one RunningStat object
        $first = new RunningStat();
        foreach( $sets[0] as $point ) {
            $first->push( $point );
        }

        // Accumulate the second half into another RunningStat object
        $second = new RunningStat();
        foreach( $sets[1] as $point ) {
            $second->push( $point );
        }

        // Merge the second RunningStat object into the first
        $first->merge( $second );

        $this->assertEquals( count( $first ), count( $this->points ) );
        $this->assertEquals( $first, $expected );
    }
}