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))) -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: not available URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20100815/6064ed25/attachment.pl>