(Reported by Søren Højsgaard) Looks like update.formula is stripping of parentheses in cases where they shouldn't be
> update.formula (Reaction ~ Days + (Days | Subject), . ~ . + I(Days^2)) Reaction ~ Days + Days | Subject + I(Days^2) Notice that the right hand side is interpreted with the bar at the root of the parse tree, as in (Days + Days) | (Subject + I(Days^2)): > f <- update.formula (Reaction ~ Days + (Days | Subject), . ~ . + I(Days^2)) > f[[3]] Days + Days | Subject + I(Days^2) > f[[3]][[1]] `|` This confuses lmer() rather badly: library(lme4) example(lmer) update(fm1,formula = . ~ . + I(Days^2)) ------> Error in x[[2]] : object is not subsettable Error in model.matrix(eval(substitute(~T, list(T = x[[2]]))), frm) : unable to find the argument 'object' in selecting a method for function 'model.matrix' -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel