[R] Unbalanced Mixed Linear Models With Nested Stratum

[JaFF]

Hi bbolker,


bbolker wrote:
> 
> Doesn't "treatment" appear in fixed effects somewhere?  Perhaps you mean
> (Treatment+Period+Dose):Eye?

Apologies for the confusion. What you referred to as "Treatment", I called
"Dose" in my post. So in your terms, to avoid confusion, the fixed effects
are (Subject + Period + Treatment):Eye. 


bbolker wrote:
> 
> JaFF <el.romaro <at> gmail.com> writes:
> Do you really want interactions only (:) rather than crossing (*)
> for the fixed effects? You will get a model with the same number of
> parameters either way, but parcelled out among effects differently.
> 
I know it may not seem as the most natural of choices, but we are fairly
certain of the random effects - they contain interactions only. 

Could you please explain how does "subject:period + subject:period:eye"
convert to "eye|subject:period"? What would "A:B:C + A:B:D:E + C" be in the
function specification, for example?

Also, the line
fit = lmer(ms ~ (subject + period + dose):eye + (eye|subject:period), data =
sub)
crashes my R with a runtime error. "ms" is one of the response variables I'm
testing it on. I wanted to try it on earlier versions of R, but the package
"lme4a" fails to install on 2.10.1, even though its pre-requisites ("minqa"
and "MatrixModels") install fine. So I guess we'll have to find a way to
make it work on 2.12.1 - the version I'm using. GenStat managed to analyse
the same data just fine, so it's not a problem with the data.

Thank you for your time.

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