How can parameter estimates be extracted from a LMEM which includes VarIdent and corAR1?
Hi Karen, I understand that you can use the intervals function for example intervals(model1, which="fixed") this will still provide differences so you would have to relevel your factors, and re run the model to get all the parameter estimates. If this is incorrect (anyone?) then feel free to correct me. Cheers Chris
On 15 Jul 2011, at 23:00, Lisa Stevens wrote:
Dear All, I was wondering if anyone knows a way to reliably extract parameter estimates from a LMEM where VarIdent and corAR1 are necessary. Here is the full model I am currently working with: model1<-lme(asin(max_cover/100)~1+provenance*lifeform*year_trt*N*P*K,method="ML",random=~1|site/plot,weights=varIdent(form=~1|lifeform), na.action=na.exclude, correlation=corAR1(form=~as.numeric(year_trt)|site/plot), data=dat1) The two lifeforms I am working with are graminoids and forbs, and the experiment is a full factorial fertilization experiment that has been conducted at 26 sites. Max_cover represents 16 species and their response to fertilization. Because I am hypotheses testing, I have simplified the model using LRT and I have found a significant four-way interaction and these trends follow the results shown in the raw data. I used REML and LRT to test VarIdent and the autocorrelation with treatment year and both are necessary. Is there a method for calculating parameter estimates from such a complex model for a designed experiment? If there isn't, does anyone have any suggestions on methods or approaches I could use to get around this issue? Thank you very much for any help or advice in advance. Best wishes, Karen [[alternative HTML version deleted]]
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Dr. Christopher Philipson Institute of Evolutionary Biology and Environmental Studies, Winterthuerstrasse 190, CH-8057, Zurich Tel: 00 41 44 635 61 29 Fax: 00 41 44 635 57 11 christopher.philipson at ieu.uzh.ch