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Gamma

by

Paul Godfrey (view profile)

 

06 Jun 2003 (Updated )

Compute a very accurate Gamma function over the entire complex plane.

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Description

A very accurate complex Gamma function valid over the entire complex plane. This function is more accurate than MATLAB's own real only Gamma function.

Acknowledgements

This file inspired Variable Order Derivatives.

MATLAB release MATLAB 6.0 (R12)
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Comments and Ratings (9)
24 Feb 2015 G. Merchant

Loss of accuracy in complex plane:

Using this routine:
gamma(-2-2e-7 i)=0.462366678321968 + 2499999.99999981i

Using backwards recursion:
gamma(0-2e-7 i)=-0.577215664901504 + 4999999.99999981i
gamma(-1-2e-7i)=gamma(-2e-7i)/(-1-2e-7i) =-0.577215664901504 + 4999999.99999981i
gamma(-2-2e-7i)=gamma(-1-2e-7i)/(-2-2e-7i)=0.461392167549202 + 2499999.99999982i

Note that the real part agree for only 2 digits. The second calculation based on backwards recursion agrees Mathematica and Fortran. Look for discussion on Google Groups by Krishna Myneni.
Is it possible to fix this issue?

Comment only
23 May 2012 Marzieh  
28 Oct 2011 Jacques Burrus

Thank you!

05 Jun 2009 Slimane Grine

Thanks. Very useful!

18 Jan 2009 Deepak

Deepak (view profile)

Its so lovely to see this function on the first search.
Extremely handy.
Please post some references as well for the theory.

10 Apr 2006 Matteo Borghi  
22 Mar 2006 Rudi Fruehwirth

Very useful!

31 Jan 2006 Bill Davidson

Thank you. Excellent. It is a handy function to have around.

09 Nov 2005 hugues de chatellus  

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