public function __construct(array $samples, array $stats = [])
{
if (count($samples) < 1) {
throw new \LogicException('Cannot create a distribution with zero samples.');
}
$this->samples = $samples;
$this->closures = ['min' => function () {
return min($this->samples);
}, 'max' => function () {
return max($this->samples);
}, 'sum' => function () {
return array_sum($this->samples);
}, 'stdev' => function () {
return Statistics::stdev($this->samples);
}, 'mean' => function () {
return Statistics::mean($this->samples);
}, 'mode' => function () {
return Statistics::kdeMode($this->samples);
}, 'variance' => function () {
return Statistics::variance($this->samples);
}, 'rstdev' => function () {
$mean = $this->getMean();
return $mean ? $this->getStdev() / $mean * 100 : 0;
}];
if ($diff = array_diff(array_keys($stats), array_keys($this->closures))) {
throw new \RuntimeException(sprintf('Unknown pre-computed stat(s) encountered: "%s"', implode('", "', $diff)));
}
$this->stats = $stats;
}
public function testStandardError()
{
$stats = new Statistics();
$sets = $this->getSetData();
foreach ($sets as $name => $data) {
$stats->set($name, $data['set']);
$this->assertEquals($data['variance'], $stats->variance($name), 'Set ' . $name . ' variance()');
}
}
public function testVariance()
{
//
// Sample (default)
//
//
// Integers
//
$values = [2, 4, 4, 4, 5, 5, 7, 9];
$sample = true;
$result = Statistics::variance($values, $sample);
$expected = 4.571429;
$this->assertEquals($expected, $result, '', pow(10, -4));
//
// Floats
//
$values = [0.0, 0.25, 0.25, 1.25, 1.5, 1.75, 2.75, 3.25];
$sample = true;
$result = Statistics::variance($values, $sample);
$expected = 1.428571;
$this->assertEquals($expected, $result, '', pow(10, -4));
//
// Population
//
//
// Integers
//
$values = [2, 4, 4, 4, 5, 5, 7, 9];
$sample = false;
$result = Statistics::variance($values, $sample);
$expected = 4;
$this->assertIdentical($expected, $result);
//
// Floats
//
$values = [0.0, 0.25, 0.25, 1.25, 1.5, 1.75, 2.75, 3.25];
$sample = false;
$result = Statistics::variance($values, $sample);
$expected = 1.25;
$this->assertIdentical($expected, $result, '', pow(10, -4));
}
