Hi all, I am attempting to use the language R for analyzing mixed models. I have encountered a syntax problem, and can't seem to get the code right. If someone else is using R for the same purpose (specifically using the "lme" package), I think you'll be able to answer my question easily. Once I've got this figured out, I will post another message with a kind of quick how-to on getting started with complex models in R, as I think there are other people that would like to use R but have been intimidated by the learning curve. Anyway, this is the question:
The model I want to run has the following factors: Host (fixed) Sire (random) Dam nested within Sire (random) Host * Sire (random) Host * Dam within Sire (random) Without the interactions I have: hogmodel = lme(gain ~ host, random = ~1|sire/dam) If I understand correctly, that "sire/dam" term gives me both Sire and Dam within Sire as random factors. OK, so now I want to add the two interactions (listed above)... In SAS, I would just enter them as random factors, but I can't seem to make that work. I think I need to make a list that includes Sire/Dam, Host:Sire, and Host:Sire/Dam. Two questions: 1) Is it sufficient to have simply Host:Sire/Dam in order to code for both interactions (host*sire and host*dam-within-sire)? 2) In any event, WHAT IS THE SYNTAX FOR MAKING A LIST OF RANDOM FACTORS (as opposed to the single random factor, which I was able to enter correctly)? I have looked in section 1.3 of Pinheiro&Bates, which was helpful, but I wasn't able to answer my question. --Matt - - - - - - Matthew L Forister Department of Ecology and Evolution State University of New York at Stony Brook 650 Life Sciences Building Stony Brook, New York 11794-5245 Email: [EMAIL PROTECTED] Webpage: http://life.bio.sunysb.edu/~forister/ Lab phone: (631) 632-8609 Fax: (631) 632-7626 - - -
