Wrong list! Post on r-sig-mixed-models instead of here. However, this is really not an R question. It appears that you are looking for remote statistical consulting, which I consider rather hazardous. Sort of like having a virtual thesis advisor. I believe you would be better off talking with your local statistician/statistical expert.
-- Bert On Sat, Jul 28, 2012 at 4:58 AM, Nathan Ranc <nathan.r...@gmail.com> wrote: > Dear all, > > I make habitat suitability models for animal species. The purpose of my > research is to investigate the accuracy of different models. > > I clearly have a nested design: > > - accuracy_measure -> response variable > - 2 model types (model_type) -> fixed effect > - 230 species (species) -> random effect > - 10 replicates/species (replicate) -> random effect > - 10 subreplicate/replicate -> observation > > So I have: 10*10*230 observations/model, identified as > speciesID_replicate_subreplicate (species_ID ranging 1:230, replicate 1:10 > and subreplicate 1:10) > > One could think about such mixed-effect model: > > my.model<-lme(fixed = accuracy_measure~model_type, random = > ~1|species/replicate) > > I do not expand here into model simplification nor if it is best to use lme > or lmer, YET... but here are more conceptual questions > > 1) my replicates & subreplicates are paired in the sense that they come > from the same split of the data. As an example for species X, the 20 > observations of replicate1 of model A and B (10 for A and 10 for B) are > linked by a same data split which is likely to influence my accuracy > measure. In the same way the 2 observations replicate1_subreplicate2 of > model A and B (1 for A and 1 for B) are also linked. Is there a way to > introduce such pairing in a mixed effect model? > > 2) several continuous covariates, attributes of species (number of points > for modelization, size in km2 of the range) may influence the measures of > accuracy and I may be interested in investigating those effects. How could > I include a covariate in such model? How should I strucutre it given that > there are species covariates (high order of nesting)? > > I hope that my questions are relevant! > Thank you very much in advance for your help! > > > Nathan > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.