Dear Mike,

Thank you very much for the timely, helpful response. My apologies for the
delay in responding - I have been in the field.


On 5/28/08, Mike Dunbar <mdu@ceh.ac.uk> wrote:
>
> Dear James
>
> Some quick initial comments.
>
> A. You are probably trying to make a much too complex model. I think what
> you want is:
>
> lmer(response ~ snow*warm*year (1|plot), cass))
>
> As plot is the only random effect, all the others are fixed.


I appreciate the simplicity of the model you have suggested. After reviewing
both Pinheiro & Bates and West, I was initially taking a more rigid approach
to developing my model following the examples in the texts.

B. Are you sure there is likely to be a measurable autoregressive structure
> to the time series data beyond that which is accounted for by the plot
> random effect. Just looking at the data listing, there are only three years
> (1995, 2000, 2007), or is this a sub-sample? With only three years, and
> these not being sequential years, you may be asking too much of your data.


 This is not a sub-sample - I only have 3 years of data. I assumed that if I
were to include a repeated measures factor in my model, that I'd need to
supply a covariance structure.


C. I might be missing something but are you really interested in year as a
> fixed effect? With this included, are there any degrees of freedom left for
> the residual error, you'll need to get your replication from somewhere. Be
> warned that lmer does seem to give results even when all dfs are used up by
> fixed effects and their interactions (I'm not sure why), but you need to be
> able to judge that you have not fitted a sensible model.


 I am interested in change over time so I need "time" as a fixed factor. I
can run the model you have suggested as a lme function too but my dfs seem
ok for this analysis.


> cheers
>
> Mike


 Using this model in an lme function, I have been unable to identify Type
III SS rather than Type I. Is there a straightforward way to obtain Type III
SS?

 Thanks again for the advice and comments - I appreciate them.

James

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