From Ted.Harding at manchester.ac.uk  Mon Mar 30 23:28:54 2009
From: Ted.Harding at manchester.ac.uk ( (Ted Harding))
Date: Mon, 30 Mar 2009 22:28:54 +0100 (BST)
Subject: [Rd] Gamma funtion(s) bug
In-Reply-To: <49D12D9F.1000203@stats.uwo.ca>
Message-ID: <XFMail.090330222854.Ted.Harding@manchester.ac.uk>

On 30-Mar-09 20:37:51, Duncan Murdoch wrote:
> On 3/30/2009 2:55 PM, (Ted Harding) wrote:
>> On 30-Mar-09 18:40:03, Kjetil Halvorsen wrote:
>>> With R 2.8.1 on ubuntu I get:
>>>> gamma(-1)
>>> [1] NaN
>>> Warning message:
>>> In gamma(-1) : NaNs produced
>>>> lgamma(-1)
>>> [1] Inf
>>> Warning message:
>>> value out of range in 'lgamma'
>>> 
>>> Is'nt the first one right, and the second one (lgamma)
>>> should also be NaN?
>>> Kjetil
>> 
>> That is surely correct! Since lim[x->(-1)+] gamma(x) = +Inf,
>> while lim[x->(-1)-] gamma(x) = -Inf, at gamma(-1) one cannot
>> choose between +Inf and -Inf, so surely is is NaN.
> 
> But lgamma(x) is log(abs(gamma(x))), so it looks okay to me.
> 
> Duncan Murdoch

Oops, yes! That's what comes of talking off the top of my head
(I don't think I've ever had occasion to evaluate lgamma(x)
for negative x, so never consciously checked in ?lgamma).

Thanks, Duncan!
Ted.

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Date: 30-Mar-09                                       Time: 22:28:52
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[Rd] Gamma funtion(s) bug
 (Ted Harding