[R] lme nesting/interaction advice

[Kingsford Jones]

On Fri, May 9, 2008 at 4:04 AM, Federico Calboli
<f.calboli at imperial.ac.uk> wrote:
>>
>> Note that random can be a list:
>>
>> "a one-sided formula of the form ~x1+...+xn, or a pdMat object with a
>> formula
>> (i.e. a non-NULL value for formula(object)), or a list of such formulas or
>> pdMat
>> objects. "
>
> If you can translate that into *informative* English I'd be grateful. I have
> the Pinheiro and Bates book under my nose now, and I suspect it's pretty
> more extensive that the helpfile, but it's still nowhere close to providing
> a straigtforward answer to my question.
>

Federico,

I think you'll be more likely to receive the type of response you're
looking for if you formulate your question more clearly.  The
inclusion of "commented, minimal, self-contained, reproducible code"
(as is requested at the bottom of every email sent by r-help) is an
effective way to clarify the issues.  Also, when asking a question
about fitting a model it's helpful to describe the specific research
questions you want the model to answer.

I'll offer my interpretation of your study design so you can see where
questions might arise.
It sounds like you have protein measures (on how many units?) at
various levels of 'male' (which at first you described as
presence/absence, but later as continuous - also you descibed 'male'
as fixed and continuous but then entered it in the formula as though
it were a random grouping factor), within the second level of
'selection' (e.g. large1), within the first level of selection (e.g.
large), within a random block (what are the blocks?)  within a random
month.  Is this right -- multiple observations within 4 levels of
nesting - some of which are random and some fixed?

Finally, I'll point out that there's an R list dedicated to mixed
models, with a particular focus on the lmer function, which might be
the right tool for your analyses (
https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models ).


Kingsford Jones



> Cheers,
>
> Federico
>
>
> --
> Federico C. F. Calboli
> Department of Epidemiology and Public Health
> Imperial College, St Mary's Campus
> Norfolk Place, London W2 1PG
>
> Tel  +44 (0)20 7594 1602     Fax (+44) 020 7594 3193
>
> f.calboli [.a.t] imperial.ac.uk
> f.calboli [.a.t] gmail.com
>
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>