Hi Jari,

Thanks for you clarify about the ortogonality of metaMDS scores :-)
Manuel, sorry for my mistake.

Cheers,

Miltinho




2008/6/12, Jari Oksanen <jari.oksanen@oulu.fi>:
>
> On Thu, 2008-06-12 at 10:36 -0300, Miltinho Astronauta wrote:
> > Hi Manuel,
> >
> > As Prof. Jari Oksanen anwered about the metaMDS, permit me comment about
> the
> > usage (or not usage) of NMDS method to reduce the dimensionality of your
> > landscape metrics. I think that your are planning keep the firsts
> dimensions
> > for other analyses. Case yes, and in the case you use the axis on
> > regression, if need to be care because the axis 1, 2 etc are not
> ortogonal,
> > and the results could be a little bit difficult of explain. There are
> three
> > papers very interesting on this regard of choice (or reduction of the
> > number) of landscape metrics:
> >
> Howdy Folks,
>
> In fact, the metaMDS ordination scores are orthogonal (because they are
> orthogonalized within metaMDS). You can see this with:
>
> cor(scores(mymetaMDSresult)) # or with
> crossprod(scores(mymetaMDSresult))
>
> This does not mean that I would recommend using these dimensions in any
> regression type analysis: you need all NMDS axes to span the space for
> which the solution is optimized, and you can't tear off an axis from the
> ordination. That is the reason why vegan has other tools than regression
> to inspect the results (ordisurf, envfit).
>
> cheers, jari oksanen
> --
> Jari Oksanen -- Dept Biology, Univ Oulu, FI-90014 Oulu, Finland
> email jari.oksanen@oulu.fi, homepage http://cc.oulu.fi/~jarioksa/
>
>

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