/// <summary>
/// Power series for incomplete beta integral; formerly named <tt>pseries</tt>.
/// Use when b*x is small and x not too close to 1.
/// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static double powerSeries(double a, double b, double x) throws ArithmeticException
internal static double powerSeries(double a, double b, double x)
{
double s, t, u, v, n, t1, z, ai;
ai = 1.0 / a;
u = (1.0 - b) * x;
v = u / (a + 1.0);
t1 = v;
t = u;
n = 2.0;
s = 0.0;
z = MACHEP * ai;
while (Math.Abs(v) > z)
{
u = (n - b) * x / n;
t *= u;
v = t / (a + n);
s += v;
n += 1.0;
}
s += t1;
s += ai;
u = a * Math.Log(x);
if ((a + b) < MAXGAM && Math.Abs(u) < MAXLOG)
{
t = GammaFunctions.gamma(a + b) / (GammaFunctions.gamma(a) * GammaFunctions.gamma(b));
s = s * t * Math.Pow(x, a);
}
else
{
t = GammaFunctions.logGamma(a + b) - GammaFunctions.logGamma(a) - GammaFunctions.logGamma(b) + u + Math.Log(s);
if (t < MINLOG)
{
s = 0.0;
}
else
{
s = Math.Exp(t);
}
}
return(s);
}
