Date: Sat, 14 Sep 1996 20:47:41 -0700 (PDT) From: Thomas Lumley <thomas@biostat.washington.edu> To: r-testers <r-testers@stat.math.ethz.ch> Subject: R-alpha: terms In-Reply-To: <Pine.SUN.3.91.960913113316.19284G-100000@chekov> terms.formula() does not do the same thing as in S. In S it returns a list with a component corresponding to each term in the RHS of the formula. In R there is only one component for the RHS. This is important in including things like offsets, weights, strata and clusters in formulas -- they need to be removed from the formula after the model.frame is constructed but before the model.matrix is constructed. In S these things can be located in the formula using the "specials" facility (which works fine in R) and then removed by subsetting. Removing them after the matrix has been made is much messier as it involves knowing how many columns correspond to each term in the formula. thomas lumley =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- r-testers mailing list -- To (un)subscribe, send subscribe or unsubscribe (in the "body", not the subject !) To: r-testers-request@stat.math.ethz.ch =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-