[R] as.formula and lme ( Fixed effects: Error in as.vector(x, "list") : cannot coerce to vector)
Douglas Bates
bates at stat.wisc.edu
Fri Feb 23 22:01:34 CET 2001
"Dieter Menne" <dieter.menne at menne-biomed.de> writes:
> Using a formula converted with as.formula with lme leads
> to an error message. Same works ok with lm, and with
> lme and a fixed formula.
>
> # demonstrates problems with lme and as.formula
> demo<-data.frame(x=1:20,y=(1:20)+rnorm(20),subj=as.factor(rep(1:2,10)))
> demo.lm1<-lme(y~x,data=demo,random=~1|subj)
> print(summary(demo.lm1))
> newframe<-data.frame(x=1:5,subj=rep(1,5))
> predict(demo.lm1,newframe,level=0)
>
> fma<-as.formula("y~x")
> demo.lm<-lm(fma,data=demo) # ok
> predict(demo.lm,newframe,level=0) # ok
> demo.lm2<-lme(fma,data=demo,random=~1|subj) # looks ok, but isn't
> print(summary(demo.lm2))
>
> #Fixed effects: Error in as.vector(x, "list") : cannot coerce to vector
> #predict(demo.lm2,newframe,level=0) # does not work
Thanks for the detailed report. I can reproduce the problem. It
appears that there needs to be an eval early in the lme function so it
stores the formula for the fixed effects, not the name of the formula.
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