SetDistributionParameters(
int alpha,
int beta
)
{
if (!IsValidParameterSet(alpha, beta))
{
throw new ArgumentException(Properties.Resources.ArgumentParameterSetInvalid);
}
_alpha = alpha;
_beta = beta;
_chiSquaredAlpha.SetDistributionParameters(alpha);
_chiSquaredBeta.SetDistributionParameters(beta);
double alphaHalf = 0.5 * alpha;
double betaHalf = 0.5 * beta;
_alphabeta = (double)beta / (double)alpha;
_pdfScaleLn =
alphaHalf * Math.Log(alpha)
+ betaHalf * Math.Log(beta)
- Fn.BetaLn(alphaHalf, betaHalf);
_pdfExponent1 = alphaHalf - 1.0;
_pdfExponent2 = -alphaHalf - betaHalf;
}
SetDistributionParameters(
int degreesOfFreedom
)
{
if (!IsValidParameterSet(degreesOfFreedom))
{
throw new ArgumentException(Properties.Resources.ArgumentParameterSetInvalid, "degreesOfFreedom");
}
_degreesOfFreedom = degreesOfFreedom;
_chiSquareDistribution.SetDistributionParameters(degreesOfFreedom);
double a = 0.5 * (_degreesOfFreedom + 1);
double nLn = Fn.GammaLn(a);
double dLn1 = Math.Log(Math.Sqrt(Math.PI * _degreesOfFreedom));
double dLn2 = Fn.GammaLn(0.5 * _degreesOfFreedom);
_exponent = -a;
_factor = Math.Exp(nLn - dLn1 - dLn2);
_summand = Fn.BetaRegularized(0.5 * _degreesOfFreedom, 0.5, 1);
}
