I am trying to make the switch from SAS, and I have a fairly elemental problem with syntax using the nlme package for analyzing mixed models. There was a previous question on this topic posted to this list, so I apologize for redundancy, but I didn't understand the advice given to that inquiry. The model I want to run has the following factors:
Dam nested within Sire (random)
Host * Sire (random)
Host * Dam within Sire (random)
So 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:
I have looked in section 1.3 of Pinheiro&Bates, which was helpful, but I wasn't able to answer my question. Thanks in advance, your help will keep me from running back to SAS!
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