[Help-gsl] Re: Incomplete Beta function for negative b ?

[Rodney Sparapani]

Lionel B wrote:
> Greetings,
>
> I need values of gsl_sf_beta_inc (double a, double b, double x) for 0 < 
> a < 1, -1 < b < 0. The incomplete Beta function is, as far as I know, 
> well-defined in this case.
>
> I'm a bit stumped - haven't managed to find any identities involving 
> B(z;a,b) that work for me here...

Hi Lionel:

I stared at that for way too long before I tried it with Mathematica.
It turns out that the result is based on Hypergeometric 2F1 which are
available in GSL as well.

Rodney