Re: [R] lme: random effects of a quadratic term

From: Montse Rue <montse.rue_at_gmail.com>
Date: Sun 27 Mar 2005 - 03:16:49 EST

Thanks! I already tried it, but then I have problems with the augPred values. I get straight lines instead of quadratic lines when plotting the augPred values.

What can I do?

Montse

On Sat, 26 Mar 2005 09:39:07 +0000 (GMT), Prof Brian Ripley <ripley@stats.ox.ac.uk> wrote:
> On Sat, 26 Mar 2005, Montse Rue wrote:
>
> > I am estimating the following model:
> >
> > so2.lme<-lme(so2~1+I(alcadakm^2)+dia,data=subjectes2,na.action=na.omit)
> >
> > And when I try to plot the random effects of the quadratic term with
> > respect to a covariate (mam) I get an error:
> >
> >> so2.lmeRE<-ranef(so2.lme,augFrame=T)
> >> plot(so2.lmeRE,form=I(alcadakm^2)~mam)
> > Error in plot.ranef.lme(so2.lmeRE, form = I(alcadakm^2) ~ mam ) :
> > Only single effects allowed in left side of form.
> >
> > Any suggestion?
>
> Try renaming the variable, e.g. alcadakm2 = alcadakm^2, and refit.
>
> NB: this is not `a quadratic term' but a transformed variable, since you
> used I().
>
> --
> Brian D. Ripley, ripley@stats.ox.ac.uk
> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
> University of Oxford, Tel: +44 1865 272861 (self)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595
>



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