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## gammainc & GSL

**From**: |
Teemu Ikonen |

**Subject**: |
gammainc & GSL |

**Date**: |
Sun, 8 Oct 2000 02:36:26 +0300 (EET DST) |

I had some problems with the function gammainc which gives wrong results
with large argument values (see my bugreport in bug-octave). When
investigating further I found out that the reason was that Octave is
trying to calculate gammainc by calling a fortran routine from SLATEC for
a slightly different form of the function (Tricomis form,
x^-a * gammainc(x, a)) and then correcting the result, which fails with
large a and x.
I tried to dug a real implementation from the net and found a nice looking
one from GNU scientific library [1]. Adding GSL routines to Octave
isn't trivial because of GSL's error handling and other supporting
functions which would have to be changed to comply with Octave, but GSL
contains a lot of useful code (in C!), especially in the special functions
section, so we could have quite a lot more functionality as a result.
Now if I start to integrate GSL into libcruft, is there any chance that
the modifications could be included in the Octave distribution?
Teemu
[1] http://sources.redhat.com/gsl/

**gammainc & GSL**,
*Teemu Ikonen* **<=**