[WP34s] Regularized incomplete Beta function

[Paul Dale]

(05-09-2014 09:06 PM)Dieter Wrote:  I am not very good at finding the code of a particular 34s function on Sourceforge, so this is what I assume:...

The function is decNumberGammap in decn.c line 2164. You assumptions are correct.

I've fixed the zero return to give a best guess return instead and increased the iteration counts which will help but won't avoid this issue.


Now to try to find a more robust algorithm. The GSL version has a third path for special argument values (for performance I suspect) but seems to use the same algorithm for the two main paths. It has an explicit failure case when it estimates that too many iterations will be required. I've seen the series and CF approaches used by other libraries too.


- Pauli