Hi Florian and others who added their advice. Thank you very much! For clarification, my response variable is really a proportion - number of occupied sites from a limited set of suitable sites, therefore not binomial (0/1). Actually, nearly half of the species (cases) have response = 0, therefore I cannot use simple logit transformation. But maybe it would make sence to perform logistic regression with success/failure in colonization as a response and for comparison try linear regression only with successful colonizers. Thanks a lot again to push me forward Best Jana ________________________________________ Odesílatel: Florian Boucher [floflobouc...@gmail.com] Odesláno: 26. ledna 2016 17:34 Komu: Knappová Jana Kopie: r-sig-phylo@r-project.org Předmět: Re: [R-sig-phylo] multiple regression with binomial distribution
Hi Jana, If your data are proportions, you might want to model their logit, ie log(X/(1-X)), rather than their raw value. You can then use PGLS in the same manner as you did. An ML value of 0 for lambda indicates that you are actually fitting a non-phylogenetic model, but it is safer to allow for lambda to vary in case there would be signal in the residuals of the regression. If your data are 0/1, then you should rather use phylogenetic logistic regression. This is implemented for example in the 'phyloglm' function in the R package 'phylolm'. Cheers, Florian 2016-01-26 16:16 GMT+01:00 Knappová Jana <jana.knapp...@ibot.cas.cz<mailto:jana.knapp...@ibot.cas.cz>>: Hi everyone, I am not very familiar with phylogenetics, but i would like to incorporate it somehow into my work and i appreciate any suggestions. Is it possible to use any kind of phylogenetically informed analysis in case of multiple regression (one response ~ multiple predictors) in case I assume binomial distribution of response variable? I try to explain species occurrence (proportional data) by a couple of species traits. I tried pgls function from "caper" R package, but I am not sure about it. Generally, it seems that there is not strong signal in my data, when I used lambda="ML" than lambda was set to zero. Thanks Jana Knappová Botanický ústav AV ČR, v. v. i. | Institute of Botany of the CAS Zámek 1, 252 43 Průhonice | Zamek 1, CZ-25243 Pruhonice Česká republika | Czech Republic jana.knapp...@ibot.cas.cz<mailto:jana.knapp...@ibot.cas.cz> www.ibot.cas.cz<http://www.ibot.cas.cz> www.pruhonickypark.cz<http://www.pruhonickypark.cz> Telefon: 271015401, 737375227 | Phone: +420-271015401<tel:%2B420-271015401>, 737375227 Fax: 271015105 | Fax: +420-271015105<tel:%2B420-271015105> _______________________________________________ R-sig-phylo mailing list - R-sig-phylo@r-project.org<mailto:R-sig-phylo@r-project.org> https://stat.ethz.ch/mailman/listinfo/r-sig-phylo Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/ -- Florian Boucher Postdoctoral researcher, Institute of Systematic Botany, Zürich _______________________________________________ R-sig-phylo mailing list - R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/
