Hi Bert, Thanks for the model selection philosophy! It’s definitely not a perfect world in terms of trying to understand the “truth", but I find that there are so many opinions about how to do model selection that I just choose one and go with it :)
My best, Corina -- Dr. Corina Logan Leverhulme Early Career Research Fellow Department of Zoology University of Cambridge [email protected] www.CorinaLogan.com On Jul 18, 2015, at 21:26, Bert Gunter-2 [via R] <[email protected]> wrote: (slightly off topic) One might also add that different model fitting criteria might produce rankings that are quite different, but with model predictions that are very similar. This reflects the inconvenient reality that empirical models are merely data interpolators and not representations of "truth." Ergo quite different looking models might fit essentially equally well, the differences in fits and therefore rankings being nothing more than noise. Cheers, Bert Bert Gunter "Data is not information. Information is not knowledge. And knowledge is certainly not wisdom." -- Clifford Stoll On Sat, Jul 18, 2015 at 10:03 AM, Ben Bolker <[hidden email] <x-msg://4/user/SendEmail.jtp?type=node&node=4710033&i=0>> wrote: > Corina <itsme <at> CorinaLogan.com> writes: > >> >> Hello, >> I am running my full model (fm) through lmer() and MCMCglmm() using the >> default settings: >> >> model.lmer <- lmer(fm) >> model.MCMCglmm <- MCMCglmm(fm) >> > > [snip] > >> However, when I run the models through dredge(): >> >> dredge(model.lmer) >> dredge(model.MCMCglmm) > >> It ranks the models very differently for lmer() and MCMCglmm() in >> the model selection tables, even though I used the default settings >> for dredge() as well (ranked by AICc). I would assume the difference >> is because lmer() uses REML and MCMCglmm() uses Bayes Rule, however >> if this is the case then why weren’t the summary outputs different >> as well? > > [snip] > > This question *might* be better on [hidden email] > <x-msg://4/user/SendEmail.jtp?type=node&node=4710033&i=1> ... > You shouldn't be comparing models with fixed effects that are fitted > with REML -- try refitting with REML=FALSE. The model comparison > functions in the lme4 package (e.g. anova()) try to stop you from > making this mistake, but I'm not sure the MuMIn::dredge does. > > ______________________________________________ > [hidden email] <x-msg://4/user/SendEmail.jtp?type=node&node=4710033&i=2> > mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > <https://stat.ethz.ch/mailman/listinfo/r-help> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > <http://www.r-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ [hidden email] <x-msg://4/user/SendEmail.jtp?type=node&node=4710033&i=3> mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help <https://stat.ethz.ch/mailman/listinfo/r-help> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html <http://www.r-project.org/posting-guide.html> and provide commented, minimal, self-contained, reproducible code. If you reply to this email, your message will be added to the discussion below: http://r.789695.n4.nabble.com/Why-does-dredge-rank-models-differently-for-lmer-and-MCMCglmm-tp4710020p4710033.html <http://r.789695.n4.nabble.com/Why-does-dredge-rank-models-differently-for-lmer-and-MCMCglmm-tp4710020p4710033.html> To unsubscribe from Why does dredge() rank models differently for lmer() and MCMCglmm()?, click here <http://r.789695.n4.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=4710020&code=aXRzbWVAQ29yaW5hTG9nYW4uY29tfDQ3MTAwMjB8LTIwNjUwNjEyMzQ=>. NAML <http://r.789695.n4.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> -- View this message in context: http://r.789695.n4.nabble.com/Why-does-dredge-rank-models-differently-for-lmer-and-MCMCglmm-tp4710020p4710130.html Sent from the R help mailing list archive at Nabble.com. [[alternative HTML version deleted]] ______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see 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.
