[R] lme: random effects of a quadratic term

[Montse Rue]

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 at 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 at 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
>