[R] lme() direction

Dieter Menne dieter.menne at menne-biomed.de
Sat Feb 7 17:34:56 CET 2009

Mike Lawrence <mike <at> thatmike.com> writes:

>Would it improve things if "type" were a continuous variable rather
>than categorical? I chose words at the extreme ends of a valence
>rating scale but I still have the raw valence ratings for each word.
> >
> > With the interaction, the extreme would be
> > summary(lme(rt~type*color*word, data=a,random=~1|id))
> >
> > or, less extreme
> >
> > summary(lme(rt~type*color+color:word, data=a,random=~1|id))
Something like

summary(lme(rt~type*color+color:as.numeric(word), data=a,random=~1|id))

(please replace as.numeric() by the raw valence, the example above it
simply wrong)

could gain you a few degrees of freedom if you are willing to accept the 
linear hypothesis. And as there is something like raw valence, one should
not throw away details about a-priori ordering in favor of a categorical


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