R help - Nov 2003 - using pdMAT in the lme function?

Hello.  I want to specify a diagonal structure for the covariance matrix
of random effects in the lme() function.

Here is the call before I specify a diagonal structure:

 
> fit2<-lme(Ln.rgr~I(Ln.nar-log(0.0011)),data=meta.analysis,
+ random=~1+I(Ln.nar-log(0.0011)|STUDY.CODE,na.action=na.omit)

 

and this works fine.  Now, I want to fix the covariance between the
between-groups slopes and intercepts to zero.  I try do do this using
the pdDiag command as follows, but it does not work:

 
> fit2<-lme(Ln.rgr~I(Ln.nar-log(0.0011)),data=meta.analysis,
+
random=pdDiag(diag(2),~1+I(Ln.nar-log(0.0011))|STUDY.CODE),na.action=na.
omit)

 

I get back an error saying that I have zero degrees of freedom.
Clearly, the syntax of the command is wrong but I can’t figure out why.
The data set (meta.analysis) is not defined as a groupedData object.

 

Any help is appreciated.

 

Bill Shipley

Associate Editor, Ecology

North American Editor, Annals of Botany

Département de biologie, Université de Sherbrooke,

Sherbrooke (Québec) J1K 2R1 CANADA

Bill.Shipley@USherbrooke.ca

 <http://callisto.si.usherb.ca:8080/bshipley/>
http://callisto.si.usherb.ca:8080/bshipley/

 


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"Bill Shipley" <bill.shipley at usherbrooke.ca> writes:
> Hello.  I want to specify a diagonal structure for the covariance matrix
> of random effects in the lme() function.
> 
> Here is the call before I specify a diagonal structure:
> > fit2<-lme(Ln.rgr~I(Ln.nar-log(0.0011)),data=meta.analysis,
> 
> + random=~1+I(Ln.nar-log(0.0011)|STUDY.CODE,na.action=na.omit)
> 
>  
> 
> and this works fine.  Now, I want to fix the covariance between the
> between-groups slopes and intercepts to zero.  I try do do this using
> the pdDiag command as follows, but it does not work:
> 
>  
> 
> > fit2<-lme(Ln.rgr~I(Ln.nar-log(0.0011)),data=meta.analysis,
> 
> +
> random=pdDiag(diag(2),~1+I(Ln.nar-log(0.0011))|STUDY.CODE),na.action=na.
> omit)
Try random=list(STUDY.CODE=pdDiag(~1+I(Ln.nar-log(0.0011))))