[R-sig-ME] Comparing mixed models

[Carlos Barboza]

Thank you Jonh for you answer
I indeed used contr.sum, contr.poly before to model definition
after that I get the same results using any names for the same factors
but, what do you exactly mean when testing for factors for differences over
the origin?
best regards
Carlos


Em qua., 19 de jun. de 2024 às 10:14, John Fox <jfox using mcmaster.ca> escreveu:

> Dear Carlos,
>
>  From ?Anova:
>
> "Warning
>
> Be careful of type-III tests: For a traditional multifactor ANOVA model
> with interactions, for example, these tests will normally only be
> sensible when using contrasts that, for different terms, are orthogonal
> in the row-basis of the model, such as those produced by contr.sum,
> contr.poly, or contr.helmert, but not by the default contr.treatment. In
> a model that contains factors, numeric covariates, and interactions,
> main-effect tests for factors will be for differences over the origin.
> In contrast (pun intended), type-II tests are invariant with respect to
> (full-rank) contrast coding. If you don't understand this issue, then
> you probably shouldn't use Anova for type-III tests."
>
> I hope this helps,
>   John
>
> --
> John Fox, Professor Emeritus
> McMaster University
> Hamilton, Ontario, Canada
> web: https://www.john-fox.ca/
> --
> On 2024-06-18 5:59 a.m., Carlos Barboza wrote:
> > [You don't often get email from carlosambarboza using gmail.com. Learn why
> this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >
> > Caution: External email.
> >
> >
> > sorry, Anova type III function form car package in R
> >
> > Em ter., 18 de jun. de 2024 às 06:59, Carlos Barboza <
> > carlosambarboza using gmail.com> escreveu:
> >
> >> Dear all,
> >> why Anova type III function gives different results if I change the
> names
> >> of a categorical factor? I suspect that is because contrast type but
> it's
> >> something strange get different results using the same data.
> >> thank you
> >>
> >> Em sáb., 7 de mai. de 2016 às 12:26, Carlos Barboza <
> >> carlosambarboza using gmail.com> escreveu:
> >>
> >>> Dear Dr. Ben Bolker
> >>>
> >>> My name is Carlos Barboza and I am a Marine Biologist from the Rio de
> >>> Janeiro University, Brazil. First it's a pleasure to again have the
> >>> opportunity to send you a message.The reason for it is a simple doubt:
> >>> Can I compare AIC from:
> >>>
> >>> 1. glmmADMB: Density ~ 1 + 1|Site
> >>>
> >>> 2. glmmADMB: Density ~ Sector + 1|Site + Cage
> >>>
> >>> Note that they have different random and fixed structures. I know that
> >>> this is not the best choice to model selection but, I think that the
> AIC
> >>> values can be compared.
> >>>
> >>> thank you very much for your attention
> >>>
> >>>
> >>>    is Cage a random effect?  Are you intentionally leaving out the
> >>> intercept in the second case (it will be included anyway unless you
> >>> use -1)?  In any case, I don't see any obvious reason you can't
> >>> compare AIC values; see
> >>>
> >>>
> https://rawgit.com/bbolker/mixedmodels-misc/master/glmmFAQ.html#can-i-use-aic-for-mixed-models-how-do-i-count-the-number-of-degrees-of-freedom-for-a-random-effect
> >>>
> >>>    Follow-ups to r-sig-mixed-models using r-project.org, please ...
> >>>
> >>> sorry, yes, cage was included only to examplify a different random
> >>> structure in the second case...it should be coded (1|Site) + (1|Cage)
> >>> yes, I know that the intercept will be included in the second model
> >>>
> >>> it's an example of comparing AIC values from mixed models with
> different
> >>> fixed and random structures:
> >>>
> >>> 1. Density ~ 1 + 1|Site
> >>>
> >>> 2. Density ~ Sector + 1|Site + 1|Cage
> >>>
> >>> comparing AIC...I beleive that both values can be compared
> >>>
> >>> again, thank you very much for your very fast message
> >>>
> >>>
> >>>
> >>>
> >>
> >> --
> >> Universidade Federal do Rio de Janeiro (UFRJ)
> >> Instituto de Biodiversidade e Sustentabilidade - NUPEM
> >> Caixa Postal 119331, CEP 27910-970
> >> Macaé, RJ, Brazil
> >> https://www.macae.ufrj.br/nupem/
> >> http://lattes.cnpq.br/3629226944950076
> >> https://scholar.google.com.br/citations?user=p-PRvd4AAAAJ&hl=pt-BR
> >> https://www.researchgate.net/profile/Carlos_Barboza3
> >>
> >
> >
> > --
> > Universidade Federal do Rio de Janeiro (UFRJ)
> > Instituto de Biodiversidade e Sustentabilidade - NUPEM
> > Caixa Postal 119331, CEP 27910-970
> > Macaé, RJ, Brazil
> > https://www.macae.ufrj.br/nupem/
> > http://lattes.cnpq.br/3629226944950076
> > https://scholar.google.com.br/citations?user=p-PRvd4AAAAJ&hl=pt-BR
> > https://www.researchgate.net/profile/Carlos_Barboza3
> >
> >          [[alternative HTML version deleted]]
> >
> > _______________________________________________
> > R-sig-mixed-models using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>
>

-- 
Universidade Federal do Rio de Janeiro (UFRJ)
Instituto de Biodiversidade e Sustentabilidade - NUPEM
Caixa Postal 119331, CEP 27910-970
Macaé, RJ, Brazil
https://www.macae.ufrj.br/nupem/
http://lattes.cnpq.br/3629226944950076
https://scholar.google.com.br/citations?user=p-PRvd4AAAAJ&hl=pt-BR
https://www.researchgate.net/profile/Carlos_Barboza3

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