[R] unexpected behaviour with sparse.model.matrix

[Jarrod Hadfield]

Hi,

I'm trying to get sparse.model.matrix to retain unused levels. I can't  
seem to get this working through the most obvious routes such as  
specifying drop.unused.levels = FALSE in the model.frame or trying to  
pass all levels in xlev,which is an argument to sparse.model.matrix  
(see code below).

Any help would be gratefully received.

Cheers,

Jarrod


fac<-factor(rep(1:10,10), levels=1:100)
mf<-model.frame(~fac, drop.unused.levels = TRUE)
mf2<-model.frame(~fac, drop.unused.levels = FALSE)

dim(model.matrix(~fac, mf))
dim(model.matrix(~fac, mf2))
dim(model.matrix(~fac, xlev=list(fac=1:10)))
dim(model.matrix(~fac, xlev=list(fac=1:100)))

dim(sparse.model.matrix(~fac, mf))
dim(sparse.model.matrix(~fac, mf2))
dim(sparse.model.matrix(~fac, xlev=list(fac=1:10)))
dim(sparse.model.matrix(~fac, xlev=list(fac=1:100)))

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