/**
Returns the cumulative distribution function, the probability of getting the test value or something below it
@param float $x The test value
@param float $k Shape parameter
@return float The probability
*/
static function getCdf($x, $k = 1)
{
return \PHPStats\Stats::lowerGamma($k / 2.0, $x / 2) / \PHPStats\Stats::gamma($k / 2.0);
}
/**
Returns the cumulative distribution function, the probability of getting the test value or something below it
@param float $x The test value
@param float $k Shape parameter
@param float $theta Scale parameter
@return float The probability
*/
static function getCdf($x, $k = 1, $theta = 1)
{
return \PHPStats\Stats::lowerGamma($k, $x / $theta) / \PHPStats\Stats::gamma($k);
}
public function test_gamma()
{
$this->assertEquals(1, round(Stats::gamma(1), 3));
$this->assertEquals(1, round(Stats::gamma(2), 3));
$this->assertEquals(1.3293326, round(Stats::gamma(2.5), 7));
$this->assertEquals(2, round(Stats::gamma(3), 5));
$this->assertEquals(6, round(Stats::gamma(4), 5));
$this->assertEquals(24, round(Stats::gamma(5), 5));
$this->assertEquals(120, round(Stats::gamma(6), 4));
}
