[R] problem with model.matrix

[Peter Dalgaard]

"Trevor Hastie" <hastie at stanford.edu> writes:

> This does not:
> 
> > model.matrix(~I(pos>3),data=data.frame(pos=c(1:2)))
> Error in "contrasts<-"(`*tmp*`, value = "contr.treatment") : 
>  contrasts can be applied only to factors with 2 or more levels

Oh yes it does:

>  model.matrix(~I(pos>3),data=data.frame(pos=c(1:2)))
  (Intercept) I(pos > 3)TRUE
1           1              0
2           1              0
attr(,"assign")
[1] 0 1
attr(,"contrasts")
attr(,"contrasts")$"I(pos > 3)"
[1] "contr.treatment"

(RedHat,SuSE,x86,amd64)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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