Date: Wed, 5 Jun 1996 11:16:53 +1200 From: Ross Ihaka <ihaka@stat.auckland.ac.nz> Message-Id: <199606042316.LAA03075@stat.auckland.ac.nz> To: r-testers@stat.math.ethz.ch Subject: R-alpha: batch mode and interactions In-Reply-To: <9606040738.AA30046@alpha.luc.ac.be> Jim Lindsey writes: > (1) As a follow-up to my problem with interactions in W&R notation, try the > following models and look at the design matrix created. The results are > surprising. > y <- rpois(9,2) # this can be anything > x1 <- gl(3,1,9) > x2 <- gl(3,3,9) > int <- as.integer(w1)*as.integer(x2) > Look at the last column of the design matrices for y~x1+x2+int and > y~x1+x2+as.integer(x1):as.integer(x2) The problem is the lack of a type check for integer vs real representations. I will fix this. I am currently giving the modeling code a going over. I hope that this will fix many/some of the problems. In particular given factors "a" and "b" with levels "A", "B" and "H", "M", "L", the corresponding coefficients (with treatment contrasts) will be aA aB bH bM bL aA.bH aB.bH aA.bM aB.bM aA.bL aB.bL with the coefficients aA, bH and interactions containing these strings dropped to ensure a full-rank design matrix. This modulo the "." seems to be what S does. Ross =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 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 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-