| private static incbd ( double a, double b, double x ) : double | ||
| a | double | |
| b | double | |
| x | double | |
| Результат | double | |
private static double incbd(double a, double b, double x)
{
double xk, pk, pkm1, pkm2, qk, qkm1, qkm2;
double k1, k2, k3, k4, k5, k6, k7, k8;
double r, t, ans, z, thresh;
int n;
double big = 4.503599627370496e15;
double biginv = 2.22044604925031308085e-16;
k1 = a;
k2 = b - 1.0;
k3 = a;
k4 = a + 1.0;
k5 = 1.0;
k6 = a + b;
k7 = a + 1.0;
;
k8 = a + 2.0;
pkm2 = 0.0;
qkm2 = 1.0;
pkm1 = 1.0;
qkm1 = 1.0;
z = x/(1.0 - x);
ans = 1.0;
r = 1.0;
n = 0;
thresh = 3.0*MACHEP;
do
{
xk = -(z*k1*k2)/(k3*k4);
pk = pkm1 + pkm2*xk;
qk = qkm1 + qkm2*xk;
pkm2 = pkm1;
pkm1 = pk;
qkm2 = qkm1;
qkm1 = qk;
xk = (z*k5*k6)/(k7*k8);
pk = pkm1 + pkm2*xk;
qk = qkm1 + qkm2*xk;
pkm2 = pkm1;
pkm1 = pk;
qkm2 = qkm1;
qkm1 = qk;
if (qk != 0) r = pk/qk;
if (r != 0)
{
t = Math.Abs((ans - r) / r);
ans = r;
}
else
t = 1.0;
if (t < thresh) return ans;
k1 += 1.0;
k2 -= 1.0;
k3 += 2.0;
k4 += 2.0;
k5 += 1.0;
k6 += 1.0;
k7 += 2.0;
k8 += 2.0;
if ((Math.Abs(qk) + Math.Abs(pk)) > big)
{
pkm2 *= biginv;
pkm1 *= biginv;
qkm2 *= biginv;
qkm1 *= biginv;
}
if ((Math.Abs(qk) < biginv) || (Math.Abs(pk) < biginv))
{
pkm2 *= big;
pkm1 *= big;
qkm2 *= big;
qkm1 *= big;
}
} while (++n < 300);
return ans;
}
