stringsAsFactors = FALSE
William Dunlap wrote:
but I'm not sure why they are being converted to factors in the first place.
I think expand.grid converts input strings to factors so they retain the order they have in the input.
Yep. These things do matter. Incidentally, I recently got burned by cooking an example using expand.grid, writing the data to a file with write.table and reading it back in during lecture with read.table. Odds ratio turned upside down...
O__ ---- Peter Dalgaard ?ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907