/// <summary>
/// Returns the value of complementary error function for the specified argument.
/// </summary>
/// <param name="x">A real number.</param>
/// <returns>The value of the complementary error function for x.</returns>
public static double Erfc(double x)
{
double absx = Math.Abs(x);
if (absx > MaxArgVal)
{
return((x > 0.0) ? 0.0 : 2.0);
}
if (absx <= Intval1)
{
return(1.0 - Erf(x));
}
if (x < 0.0)
{
return(2.0 - Erfc(-x));
}
if (absx <= Intval2)
{
return(Math.Exp(-(x * x)) * RationalFunc(erfc_p1, erfc_q1, x));
}
else
{
double xsq = x * x;
double invxsq = 1.0 / xsq;
double R = RationalFunc(erfc_p2, erfc_q2, invxsq);
double t = 1.0 / ExMath.SqrtPi + invxsq * R;
return(Math.Exp(-xsq) / x * (t - ExMath.Truncate(t)));
}
}
