public function testChiSquareSimple()
{
$this->assertEquals(1.44, PearsonChiSquare::chiSquare(array(44, 56), array(0.5, 0.5)), '', 1.0E-5);
$this->assertEquals(4.54, PearsonChiSquare::chiSquare(array(14, 21, 25), array(0.167, 0.483, 0.35)), '', 0.01);
$this->assertEquals(135.93, PearsonChiSquare::chiSquare(array(700, 790, 30, 40), array(0.54, 0.4, 0.05, 0.01)), '', 0.01);
$this->assertEquals(0.35, PearsonChiSquare::chiSquare(array(423, 133), array(0.75, 0.25)), '', 0.1);
}
/**
* Checks that resulting distribution of binary values is
* approximately same.
*
* @param string $bytes to check
*/
public static function pvalue($bytes)
{
$hist = array();
// histogram
$freq = array();
// expected frequency
$N = 256;
for ($i = 0; $i < $N; $i++) {
$hist[$i] = 0;
$freq[$i] = 1.0 / $N;
}
foreach (unpack('C*', $bytes) as $char) {
$hist[$char]++;
}
$chisqr = PearsonChiSquare::chiSquare($hist, $freq);
return PearsonChiSquare::pvalue($N - 1, $chisqr);
}
