Re: betainc and other special functions in Octave

[Michele]

On 06/10/2017 10:47 AM, Michael D Godfrey wrote:
> On 06/10/2017 02:42 AM, Rik wrote:
> > Is there a special functions Summer of Code project this year?  I 
> > thought I
> > saw some e-mails on the list about that.
> >
> > I'd like to point out bug #51157 (https://savannah.gnu.org/bugs/?51157)
> > where the betainc calculations are inaccurate for some values. I did 
> > some
> > tracing and it comes down to the Fortran routines from Slatec that are
> > used.  They were last updated in 1992, and apparently are not 
> > accurate out
> > to the 15th or 16th digit of precision.
> >
> > As a quick test, I wrote a C program that uses the GNU Scientific 
> > Library
> > to calculate betainc and it does get the more precise answer. The GSL
> > might be a way to quickly get access to other high quality special 
> > function
> > code.
> >
> > Just a thought,
> > Rik
> It would be good to include bug #44310 with this.
>
> Michael
Dear all,

I'm the guy working on the Special Functions project for GSoC. Thank you 
Rik for the hint! betainc was already in my to do list due to bug #34405 
and I saw this new bug in the tracker. Maybe I will change my timeline 
since my idea was to dedicate a week to betainc, but this new problem 
make me think I will need more time.
Regarding bug #44310, I think I can try to use the last part of the GSoC 
to work on it, but I have to discuss it with my mentors.

Michele