public static double StudentDistributionInversed(int k, double p)
{
double z;
double rk = k;
if (p is > .25 and < .75)
{
if (Math.Abs(p - .5) < Eps)
{
return(0);
}
z = IncompleteBeta.IncompleteBetaInversed(.5, .5 * rk, Math.Abs(1 - 2 * p));
var t = Math.Sqrt(rk * z / (1 - z));
return(p < 0 ? -t : t);
}
var r_flg = -1;
if (p >= .5)
{
p = 1 - p;
r_flg = 1;
}
z = IncompleteBeta.IncompleteBetaInversed(.5 * rk, .5, 2 * p);
return(__MaxRealNumber * z < rk ? r_flg * __MaxRealNumber : r_flg *Math.Sqrt(rk / z - rk));
}
