double rodbard(double x) {
// y = c*((a-x/(x-d))^(1/b)
// a=3.9, b=.88, c=712, d=44
double ex;
if (x == 0.0) ex = 5.0;
else ex = Math.exp(Math.log(x / 700.0) * 0.88);
double y = 3.9 - 44.0;
y = y / (1.0 + ex);
return y + 44.0;
}
