Re: [R] Mixed model question

From: ronggui <0034058_at_fudan.edu.cn>
Date: Sat 18 Jun 2005 - 03:48:20 EST

and the newest R-new in the www.r-project.org has an article about how to use the lmer function.

On Fri, 17 Jun 2005 08:43:41 -0700
Spencer Graves <spencer.graves@pdf.com> wrote:

> Have you also tried "lmer" in library(lme4)? This is newer and
> better in many ways. Unfortunately, I see only one example in the Help
> file, but you might be able to figure out how to use lmer from the help
> file and from the 125 hits on RSiteSearch("lmer").
>
> The definitive work on this subject, from my perspective, is Pinheiro
> and Bates (2000) Mixed-Effects Models in S and S-PLUS (Springer). This
> book is primarily how to use lme. I learned a lot from it (and from
> Doug Bates' other book with Don Watts on nonlinear regression). I
> couldn't find Pinheiro and Bates in the catalog for the library at
> Universidad de Sevilla (though Bates and Watts was listed).
>
> Feel free to submit other questions after you've considered this, but
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html first. In particular, you
> might have gotten a more helpful reply to this question if you had
> included one of your attempts with "lme", asking what you did wrong or
> what you don't understand about the results.
>
> Buena suerte,
> spencer graves
>
> Alfonso M Sanchez-Lafuente wrote:
> > Hi,
> >
> > I am new to this list as a poster, but a reader for some time.
> >
> > I've using R for several weeks now, and I have a lot of questions about
> > certain procedures. Here I go:
> >
> > I want to test if there are differences in the time spent by pollinators
> > visiting flowers of a given plant species, according to a number of
> > experimental manipulations made on those flowers. All experimental
> > manipulations (factor with 5 levels) are replicated within plants (i.e.
> > plant is my sampling unit). Further, I have two populations (two level
> > factor), and a number of pollinator groups (again, two levels, the same
> > in both populations). The response variables in the numbe of seconds
> > invested in each probe. Further, I have plant floral display as a
> > covariate, as it may influence visitation rates.
> >
> > I think I have to analyse this desing considering population, pollinator
> > group and their interaction as fixed effects, and treatment nested
> > within plant, and its interaction with population and pollinator group,
> > as random factors.
> >
> > In SAS terminology, the model looks like this:
> >
> > proc mixed data=flwfunc.visitflower covtest method=reml;
> > class site pollclass treatm plantid;
> > model time = site|pollclass flwinflor / chisq;
> > random treatm site*treatm pollclass*treatm / subject=plantid;
> > lsmeans site pollclass site*pollclass;
> > run;
> >
> > I've been successfully trying lm, but I think is not suitable for random
> > effects. Thus, I've tried lme, but no success when defining the random
> > part or trying to interpret the results...
> >
> > Any help will be welcome!
> >
>
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-- 
Department of Sociology
Fudan University,Shanghai
Blog:http://sociology.yculblog.com

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Received on Sat Jun 18 04:32:23 2005

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