[R-sig-Geo] pcnm - scaling

[Stéphane Dray]

Hi,
it is not clear for me what you mean by  "is it possible to extract a 
spatial scale describing the spatial autocorrelation (e.g. from the 
eigenvalues)?". The function scores.listw is more general and returns a 
vector $values that are equal to Moran's I (multiplyied by a constant).

Cheers,


 

robert.ptacnik at niva.no wrote:
> Dear listers,
>
> [below message was posted on R-help already, but maybe is pøaced better
> here]
>
> I am using the pcnm function (spacemakeR) to obtain eigenvectors for a
>
> spatial grid of sampling sites. These pcnm eigenvectors are then used in
>
> multivariate ordination to test where community composition follows local
>
> environment or rather shows spatial autocorrelation, and get support for
>
> apatial autocorrelation.
>
> In an RDA analysis, I can see which eigenvectors correlate most with my
>
> data, which can be interpreted that the spatial scale is rather 'fine' or
>
> 'broad' (broad in case of my data). However, is there a way to read the
> spatial scale on which the
>
> data correlates best, i.e. is it possible to extract a spatial scale
>
> describing the spatial autocorrelation (e.g. from the eigenvalues)?
>
> My data
>
>
> - irregularly spaced sampling sites, total scale ca. 2000 km, most sites
>
> few tens of km apart
>
> - i use the dfunction rdist.earth to obtain a distance-matrix of all sites
>
> prior to using pcnm
>
> Thanks !
>
> Robert
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>
>
>
>   

-- 
Stéphane DRAY (dray at biomserv.univ-lyon1.fr )
Laboratoire BBE-CNRS-UMR-5558, Univ. C. Bernard - Lyon I
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