On Tue, 29 Jul 2008, Ben Bolker wrote:
jcarmichael <jcarmichael314 <at> gmail.com> writes:
Hello.
I am attempting to duplicate a negative binomial regression in R. SAS uses
generalized estimating equations for model fitting in the GENMOD procedure.
proc genmod data=mydata (where=(gender='F'));
by agegroup;
class id gender type;
model count = var1 var2 var3 /dist=NB link=log offset=lregtm;
repeated subject=id /type=exch;
run;
Since my dataset has several observations for each subject, I need the
REPEATED statement in order to indicate dependence among observations with
the same subject ID and independence amongst those with distinct subject
IDs. The TYPE statement goes on to specify the structure of the correlation
matrix to be used (exchangeable in this case).
I would try glmmPQL in the MASS package. I don't think you
can *quite* get negative binomial regression this way, but
you can definitely get a quasipoisson model. I think exchangeable
correlation corresponds to correlation=corCompSymm() in your
glmmPQL command.
The problem here is that GLMM and GEE are not fitting the same model -- in
one the coefficients are subject-specific and in the other
population-average (see MASS4 or Diggle, Liang, Zeger +/- Heagarty).
There are several R packages for GEE, including gee, yags, geepack. The
documentation of geeglm (geepack) claims it can be used with families as
in glm(), so you could try it with MASS's negative.binomial family.
--
Brian D. Ripley, [EMAIL PROTECTED]
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@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
