[R] strange behaviour of negative binomial
Gabor Grothendieck
ggrothendieck at myway.com
Thu Jan 6 01:24:46 CET 2005
I tried it on Windows XP under both 2.0.1 and 2.1.0 and it seemed to
work both times. I issued the command:
set.seed(1)
before both runs to ensure that I was actually using the same
random numbers. I suggest you try that in all your runs too just
in case its a problem with some sets of random numbers but not
others.
dax42 <Dax42 <at> web.de> writes:
:
: 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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