internal double lbeta(double a, double b)
{
double num;
double num3;
double x = num3 = a;
if (b < x)
{
x = b;
}
if (b > num3)
{
num3 = b;
}
if (x < 0.0)
{
return(double.NaN);
}
if (x == 0.0)
{
return(double.MaxValue);
}
if (x >= 10.0)
{
num = (this.lgammacor(x) + this.lgammacor(num3)) - this.lgammacor(x + num3);
return(((((Math.Log(num3) * -0.5) + 0.91893853320467278) + num) + ((x - 0.5) * Math.Log(x / (x + num3)))) + (num3 * this.logrelerr(-x / (x + num3))));
}
if (num3 >= 10.0)
{
num = this.lgammacor(num3) - this.lgammacor(x + num3);
object obj2 = new CalcGammaLnFunction().Evaluate(new object[] { (double)x });
if (obj2 is CalcError)
{
return(double.NaN);
}
return((((((double)obj2) + num) + x) - (x * Math.Log(x + num3))) + ((num3 - 0.5) * this.logrelerr(-x / (x + num3))));
}
double num4 = EngineeringHelper.gamma(x);
double num5 = EngineeringHelper.gamma(num3);
double num6 = EngineeringHelper.gamma(x + num3);
return(Math.Log(num4 * (num5 / num6)));
}
/// <summary>
/// Returns the <see cref="T:System.Double" /> gamma distribution.
/// </summary>
/// <param name="args"><para>
/// The args contains 4 items: x, alpha, beta, cumulative.
/// </para>
/// <para>
/// X is the value at which you want to evaluate the distribution.
/// </para>
/// <para>
/// Alpha is a parameter to the distribution.
/// </para>
/// <para>
/// Beta is a parameter to the distribution. If beta = 1, GAMMADIST returns the standard gamma distribution.
/// </para>
/// <para>
/// Cumulative is a logical value that determines the form of the function. If cumulative is TRUE, GAMMADIST returns the cumulative distribution function; if FALSE, it returns the probability density function.
/// </para></param>
/// <returns>
/// A <see cref="T:System.Double" /> value that indicates the evaluate result.
/// </returns>
public override object Evaluate(object[] args)
{
double num;
double num2;
double num3;
bool flag;
double num9;
double num15;
double num16;
double num18;
double num21;
base.CheckArgumentsLength(args);
if ((!CalcConvert.TryToDouble(args[0], out num, true) || !CalcConvert.TryToDouble(args[1], out num2, true)) || !CalcConvert.TryToDouble(args[2], out num3, true))
{
return(CalcErrors.Value);
}
if (!CalcConvert.TryToBool(args[3], out flag))
{
return(CalcErrors.Value);
}
if (((num < 0.0) || (num2 <= 0.0)) || (num3 <= 0.0))
{
return(CalcErrors.Number);
}
if (!flag)
{
double d = Math.Pow(num3, num2);
if (double.IsNaN(d) || double.IsInfinity(d))
{
return(CalcErrors.DivideByZero);
}
double num5 = 1.0 / (d * EngineeringHelper.gamma(num2));
double num6 = Math.Pow(num, num2 - 1.0);
double num7 = Math.Exp(-(num / num3));
double num8 = num6 * num7;
return((double)(num5 * num8));
}
double y = 0.33333333333333331;
double num23 = 100000000.0;
double num24 = 1E+37;
double num25 = 1000.0;
double num26 = -88.0;
num /= num3;
if (num <= 0.0)
{
return(CalcErrors.Number);
}
if (num2 > num25)
{
CalcBuiltinFunction function = new CalcNormDistFunction();
num9 = (Math.Sqrt(num2) * 3.0) * ((Math.Pow(num / num2, y) + (1.0 / (num2 * 9.0))) - 1.0);
object obj2 = function.Evaluate(new object[] { (double)num9, (double)0.0, (double)1.0, (bool)true });
if (obj2 is CalcError)
{
return(obj2);
}
return((double)obj2);
}
if (num > num23)
{
return((double)1.0);
}
if ((num <= 1.0) || (num < num2))
{
object obj3 = new CalcGammaLnFunction().Evaluate(new object[] { (double)(num2 + 1.0) });
if (obj3 is CalcError)
{
return(obj3);
}
num15 = ((num2 * Math.Log(num)) - num) - ((double)obj3);
num16 = 1.0;
num21 = 1.0;
num18 = num2;
do
{
num18++;
num16 = (num16 * num) / num18;
num21 += num16;
}while (num16 > 2.2204460492503131E-16);
num15 += Math.Log(num21);
num21 = 0.0;
if (num15 >= num26)
{
num21 = Math.Exp(num15);
}
}
else
{
object obj4 = new CalcGammaLnFunction().Evaluate(new object[] { (double)num2 });
if (obj4 is CalcError)
{
return(obj4);
}
num15 = ((num2 * Math.Log(num)) - num) - ((double)obj4);
num18 = 1.0 - num2;
double num19 = (num18 + num) + 1.0;
num16 = 0.0;
num9 = 1.0;
double num10 = num;
double num11 = num + 1.0;
double num12 = num * num19;
num21 = num11 / num12;
while (true)
{
num18++;
num19 += 2.0;
num16++;
double num20 = num18 * num16;
double num13 = (num19 * num11) - (num20 * num9);
double num14 = (num19 * num12) - (num20 * num10);
if (Math.Abs(num14) > 0.0)
{
double num17 = num13 / num14;
if (Math.Abs((double)(num21 - num17)) <= Math.Min((double)2.2204460492503131E-16, (double)(2.2204460492503131E-16 * num17)))
{
break;
}
num21 = num17;
}
num9 = num11;
num10 = num12;
num11 = num13;
num12 = num14;
if (Math.Abs(num13) >= num24)
{
num9 /= num24;
num10 /= num24;
num11 /= num24;
num12 /= num24;
}
}
num15 += Math.Log(num21);
num21 = 1.0;
if (num15 >= num26)
{
num21 = 1.0 - Math.Exp(num15);
}
}
return((double)num21);
}
