Hi, Usually species richness data have very heterogeneous variance, so they are better described by a Poisson distribution than by a Gaussian. you should probably analyse your data with Generalized Linear Models using function lmer (from package lme4) and specify family=poisson.
hope this helps luisa On Wed, Feb 17, 2010 at 4:09 PM, Fons van der Plas <fonsvanderp...@gmail.com> wrote: > > Hi all, > > I'd like to compare species richness patterns of two groups with paired > observations with an extra continuous fixed effect as a covariate. Normally > I would use a standard general mixed effect model for such data, with one > group variable and a continuous variable as fixed effects, plus a random > effect for the paired observations. However, after making such a model with > the lme function, I saw that the residuals of my model were not normally > distributed and transforming them to a normal distribution does not seem to > be possible. Therefore I need a nonparametric equivalent of the lme function > to build a nonparametric mixed effect model. Does anyone know how I can do > this? Any help would be very appreciated! > -- > View this message in context: > http://n4.nabble.com/nonparametric-mixed-effect-model-tp1558728p1558728.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > -- Luisa Carvalheiro, PhD Southern African Biodiversity Institute, Kirstenbosch Research Center, Claremont & University of Pretoria Postal address - SAWC Pbag X3015 Hoedspruit 1380, South Africa telephone - +27 (0) 790250944 carvalhe...@sanbi.org lgcarvalhe...@gmail.com ______________________________________________ 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.
