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[Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma funct
From: |
Rik |
Subject: |
[Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments |
Date: |
Fri, 07 Nov 2014 16:25:51 +0000 |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:33.0) Gecko/20100101 Firefox/33.0 |
Follow-up Comment #1, bug #43551 (project octave):
I guess we should think about which form is more useful.
The Wikipedia entry for the gamma function has a nice plot of the function
(http://en.wikipedia.org/wiki/Gamma_function). The magnitude of the function
at a negative integer is infinite. But, if you choose a consistent direction,
such as always approaching the pole from the left, then the sign of the result
flips back and forth between +1 and -1. Wolfram Alpha, a.k.a Mathematica,
returns complex infinity for gamma (negative integer). A complex infinity has
infinite magnitude, but no determined phase. This is consistent with the plot
which shows that you are either getting +Inf or -Inf in the limit.
So, is it more useful to simply pick a phase (+1) and return Inf as Matlab
does? Or is it more useful to throw a NaN which will clog up downstream
calculations and indicate that we have gone beyond our ability to truly
calculate the result?
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- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, John W. Eaton, 2014/11/06
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments,
Rik <=
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, John W. Eaton, 2014/11/07
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, Rik, 2014/11/07
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, John W. Eaton, 2014/11/07
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, John W. Eaton, 2014/11/07
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, Michael Godfrey, 2014/11/07
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, Rik, 2014/11/07
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, Michael Godfrey, 2014/11/08
- [Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments, Rik, 2014/11/12