Expand description
Computes the regularized lower incomplete beta function
I_x(a,b) = 1/Beta(a,b) * int(t^(a-1)*(1-t)^(b-1), t=0..x)
a > 0, b > 0, 1 >= x >= 0 where a is the first beta parameter,
b is the second beta parameter, and x is the upper limit of the
integral.
Errors
if a <= 0.0, b <= 0.0, x < 0.0, or x > 1.0