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First TwoPlayerTrueSkillCalculator unit test passed

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Jeff Moser
2010-08-28 22:05:41 -04:00
commit 12a02b8403
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PHPSkills/TrueSkill/DrawMargin.php Normal file
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<?php
namespace Moserware\Skills\TrueSkill;
require_once(dirname(__FILE__) . "/../Numerics/GaussianDistribution.php");
use Moserware\Numerics\GaussianDistribution;
final class DrawMargin
{
public static function getDrawMarginFromDrawProbability($drawProbability, $beta)
{
// Derived from TrueSkill technical report (MSR-TR-2006-80), page 6
// draw probability = 2 * CDF(margin/(sqrt(n1+n2)*beta)) -1
// implies
//
// margin = inversecdf((draw probability + 1)/2) * sqrt(n1+n2) * beta
// n1 and n2 are the number of players on each team
$margin = GaussianDistribution::inverseCumulativeTo(.5*($drawProbability + 1), 0, 1)*sqrt(1 + 1)*
$beta;
return $margin;
}
}
?>