[R-sig-ME] How can parameter estimates be extracted from a LMEM which includes VarIdent and corAR1?

[Christopher Philipson]

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
> 
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> 
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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