From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>

Date: Sun 26 Jun 2005 - 17:04:55 EST

Date: Sun 26 Jun 2005 - 17:04:55 EST

On Sat, 25 Jun 2005, Faheem Mitha wrote:

*>
**> Hi,
**>
*

> In src/nmath/dgamma.c the comment at the top says

*>
**> * DESCRIPTION
**> *
**> * Computes the density of the gamma distribution,
**> *
**> * 1/s (x/s)^{a-1} exp(-x/s)
**> * p(x;a,s) = -----------------------
**> * (a-1)!
**> *
**> * where `s' is the scale (= 1/lambda in other parametrizations)
**> * and `a' is the shape parameter ( = alpha in other contexts).
**>
**> Maybe I'm missing something, but shouldn't the denominator be Gamma(a)
**> (since a is not necessarily an integer)?
*

\Gamma(x+1) _is_ the definition of x! for x not an integer. It has not defined x! and you have not defined Gamma(x) and I don't see one is necessarily preferable to the other. The user-level documentation uses Gamma(a) but it can refer to the definition in ?gamma.

Please see the posting guide and consider which list you use: comments in the R source code are not really end-user questions and R-devel is the appropriate place to discuss the R sources.

-- Brian D. Ripley, ripley@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.htmlReceived on Sun Jun 26 17:10:25 2005

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