use Covariance;
  
role ThisCovariance { method cov($xpop,$ypop) {
        return Covariance().Covariance($xpop,$ypop);
}
}


class Correlation does ThisCovariance {
        method BUILD() {

        }

        method correlation($xpop,$ypop) { ### These are distribution args

                my $varx = $xpop.Variance(), $vary = $ypop.Variance();
                my $cov = .cov($xpop, $ypop);

                return $cov / (sqrt($varx) * sqrt($vary));

        }
}