[R-SIG-Mac] Re: [R] strange behaviour of negative binomial

[Rob J Goedman]

Wow, there is indeed a huge difference in elapsed time for nbinom.
Almost linear with the length of x.

The non-GUI version stays around a second or so, for  length(x) == 871, 
the GUI
version takes ~25 seconds, for length(x)==8701, the GUI version takes 
~250 secs.

It seems only to occur with nbinom. Norm, binom, exp, gamma etc. all 
are within 1
or 2 seconds.

The curves I'm getting are identical though. In all runs the 2 curves 
did overlap.

Rob

On Jan 5, 2005, at 2:53 PM, dax42 wrote:

> Hi,
>
> I am sorry for the incorrect terms. Of course I mean the cumulative 
> distribution functions.
> As I just got two answers telling me my problem does not exist, I 
> tried again on a different setup - and indeed it works.
>
> So, my first run was done on a Mac OS X 10.3.7 running R 2.0.0, GUI 
> version.
> Now I tried it on the same system, only I used the R 2.0.0 on my X11, 
> not the GUI version.
>
> First setup produces the error (and is VERY slow, talking about 
> several minutes here...)
> Second works fine.
>
> Does anybody have a similar setup and could try this out as well?
> Thanks!
> Dax
>
> Am 05.01.2005 um 23:32 schrieb Peter Dalgaard:
>
>> dax42 <Dax42 at web.de> writes:
>>
>>> Dear list,
>>>
>>> I ran into a strange behaviour of the pnbinom function - or maybe I
>>> just made a stupid mistake.
>>> First thing is that pnbinom seems to be very slow. The other - more
>>> interesting one - is that I get two different curves when I plot the
>>> estimated density and the density given by pnbinom. Shouldn't it be
>>> the same?
>>> This is only the case, I think, if I use the parameter size = 1. I
>>> just tried it for size = 2 and the result seemed correct..
>>>
>>> Anyways, this is what I tried:
>>>
>>> #parameters
>>> proba<-0.001039302;
>>> s<-1;
>>>
>>> #random numbers with this distribution
>>> dom<-rnbinom(10000,s,proba);
>>>
>>> #first plot
>>> plot(ecdf(dom),do.points=FALSE);
>>>
>>> #second plot
>>> x<-seq(0,8700,0.5);
>>> lines(x,pnbinom(x,s,proba),col="red");
>>
>> Errrr... What's the problem here? The two curves look quite similar to
>> me. (And both are of course cumulative distribution functions and not
>> densities, but it doesn't sound like that is the problem.)
>>
>> -- 
>>    O__  ---- Peter Dalgaard             Blegdamsvej 3
>>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
>>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 
>> 35327918
>> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 
>> 35327907
>>
>
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