Sorry to do this to you, but questions about mixed models(especially lmer) are better handled on the mixed models list, r-sig-mixed-models . So subscribe and post this there.
Cheers, Bert On Fri, Nov 15, 2013 at 3:30 PM, Dalal Hanna <dalal.e.ha...@gmail.com> wrote: > Hi, > > I tried to post the below message and it was rejected because I hadn't yet > received my subscription to the group. > > Can it be posted now? > > Cheers, > Thanks very much for all your dedication to this project! > Dalal > > > MESSAGE I ATTEMPTED TO POST BELOW > > I am trying to code the following idea using lmer (package lme4) and > running into problems. I am also unsure that I am coding this properly and > wanted to double check, as there are not enough people in my entourage that > can do this for me. > > For individual fish i of species j in lake k, > Hgijk ~ b0j[i] + b1k[i] + b2j[i]*lengthi + ei > ei ~ N(0,s2e) > b0j ~ N(mb0,s2b0) > b1k ~ go + g1*chlorophyll-ak + eb1 > eb1 ~ N(0,s2b1) > b2j ~ N(mb2,s2b2) > > This model says that the Hg for fish i of species j from lake k is a > function of the species, the lake, and the length of the fish. The species > effects are like intercepts – the average Hg for a particular species at > average length (if the length data are centered) in an average lake – and > they come from a normal distribution. The lake effect is itself a linear > function of chlorophyll concentration, so that lakes with higher > chlorophyll can potentially have higher or lower average Hg concentrations. > The length effects vary by species, on the assumption that Hg concentration > may change with size differently in different species (which is the case in > the systems I am working in). These length effects come from a normal > distribution. > > *Problems:* > 1. My original idea was to code this as such: > > M.A4<-lmer(LogTHg~ Chlorophyll + Length+ (1 + Length|SpeciesCode) > +(1|Location), data=mercury.subset) > > -Does this function really represent the ideas I explained above? I am not > sure if Length is supposed to be included in 2 places as it is here > -When I run this model, the se.ceof() of Length always comes out to 0, > which doesn't really make sense. Any ideas why this might be happening? > > Thank you very much for taking the time to read this and providing input. > I appreciate it. > > [[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 (650) 467-7374 ______________________________________________ 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.
