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<?php
/**
* PHP Unit tests for RunningStat class.
* @covers RunningStat
*/
class RunningStatTest extends PHPUnit_Framework_TestCase {
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,
);
/**
* Verify that the statistical moments and extrema computed by RunningStat
* match expected values.
* @covers RunningStat::push
* @covers RunningStat::count
* @covers RunningStat::getMean
* @covers RunningStat::getVariance
* @covers RunningStat::getStdDev
*/
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 );
}
/**
* When one RunningStat instance is merged into another, the state of the
* target RunningInstance should have the state that it would have had if
* all the data had been accumulated by it alone.
* @covers RunningStat::merge
* @covers RunningStat::count
*/
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 );
}
}
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