[R-sig-eco] Multivariate ANOVA/repeated measures

[Gavin Simpson]

On Mon, 2011-10-10 at 09:11 -0700, Rich Shepard wrote:
> On Mon, 10 Oct 2011, Dave Roberts wrote:
> 
> >> I want to compare the results of the two sampling exercises in order to
> >> test the performance of the two sampling techniques.
> 
> >   I would try something pretty direct. Any appeal to differences in
> > dissimilarities confounds the effects with the particular
> > dissimilarity/distance matrix you use. Assuming the samples and species
> > are in the same order, and that the data.frames are the same size, you
> > might try
> 
>    I did not read the original message, so I hope you'll allow me to join the
> thread. My recommendation is to use univariate tree models, particularly a
> classification tree (for ordinal explanatory variables; i.e., ST1 and ST2).

But the response here is *multivariate* - of course, one could use Glen
De'Ath's multivariate regression trees (despite the name it is really a
constrained clustering/classification) - but I think there are better
ways of solving this particular problem. And unless one has many 100s of
observations, the model will need some sort of variance reduction
applied (via bagging, or some such) as the one fitted model is
potentially highly unstable.

G

>    This is fully, carefully, and non-technically explained in Chapter 9
> (particularly Sections 9.3 and 9.4) in Zuur, Ieno, and Smith "Analysing
> Ecological Data." For that matter, I highly recommend reading the whole
> book.
> 
> Rich
> 
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