/// @return double a random number distributed according to the receiver.
public override double Random()
{
if (_chiSquareDistribution1 == null)
{
_chiSquareDistribution1 = new ChiSquareDistribution(_dof1);
_chiSquareDistribution2 = new ChiSquareDistribution(_dof2);
}
return _chiSquareDistribution1.Random() * _dof2
/ (_chiSquareDistribution2.Random() * _dof1);
}
/// @return double a random number distributed according to the receiver.
public override double Random()
{
if (_chiSquareDistribution == null)
{
_chiSquareDistribution = new ChiSquareDistribution(_dof - 1);
}
return Generator.NextGaussian() * System.Math.Sqrt((_dof - 1) / _chiSquareDistribution.Random());
}
/// Assigns new degrees of freedom to the receiver.
/// Compute the norm of the distribution after a change of parameters.
/// @param n1 int first degree of freedom
/// @param n2 int second degree of freedom
public void DefineParameters(int n1, int n2)
{
_dof1 = n1;
_dof2 = n2;
double nn1 = 0.5 * n1;
double nn2 = 0.5 * n2;
_norm = nn1 * System.Math.Log(n1) + nn2 * System.Math.Log(n2)
- GammaFunction.LogBeta(nn1, nn2);
_incompleteBetaFunction = null;
_chiSquareDistribution1 = null;
_chiSquareDistribution2 = null;
}
