[R] using pdMAT in the lme function?

[Douglas Bates]

"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))))