public function testAbsoluteDifference()
{
// Verified with Ralf Herbrich's F# implementation
$standardNormal = new GaussianDistribution(0, 1);
$absDiff = GaussianDistribution::absoluteDifference($standardNormal, $standardNormal);
$this->assertEquals(0.0, $absDiff, '', GaussianDistributionTest::ERROR_TOLERANCE);
$m1s2 = new GaussianDistribution(1, 2);
$m3s4 = new GaussianDistribution(3, 4);
$absDiff2 = GaussianDistribution::absoluteDifference($m1s2, $m3s4);
$this->assertEquals(0.4330127018922193, $absDiff2, '', GaussianDistributionTest::ERROR_TOLERANCE);
}
