//private IncompleteBetaFunctionFraction inverseFraction;
/// Constructor method.
/// @param a1 double
/// @param a2 double
public IncompleteBetaFunction(double a1, double a2)
{
_alpha1 = a1;
_alpha2 = a2;
_logNorm = GammaFunction.LogGamma(_alpha1 + _alpha2)
- GammaFunction.LogGamma(_alpha1)
- GammaFunction.LogGamma(_alpha2);
}
/// Assigns new values to the parameters.
/// This method assumes that the parameters have been already checked.
public void DefineParameters(double shape, double scale)
{
_alpha = shape;
_beta = scale;
_norm = Math.Log(_beta) * _alpha + GammaFunction.LogGamma(_alpha);
if (_alpha < 1)
{
_b = (Math.E + _alpha) / Math.E;
}
else if (_alpha > 1)
{
_a = Math.Sqrt(2 * _alpha - 1);
_b = _alpha - Math.Log(4.0);
_q = _alpha + 1 / _a;
_d = 1 + Math.Log(4.5);
}
_incompleteGammaFunction = null;
}
/// Constructor method.
public IncompleteGammaFunction(double a)
{
_alpha = a;
_alphaLogGamma = GammaFunction.LogGamma(_alpha);
}