[GRASS-stats] Re: Correlation calculation

[Duccio Rocchini]

This is a stimulating point. testing correlation with autocorrelated data.
The reply by Roger is great! You could test additionally bootstrap methods
(rely on Brian Cade's papers). I guess that it does not solve the
autocorrelation problem actually, but ....

Further, Ingolf Kuhn has developed a number of measures of autocorrelation.
They are available in R. Just take a look at his home page.

Best!
Duccio


> > Great, this worked, thank you for your quick reply Roger. The missing
> values
> > are intended - I didn't realise that I had to specify such to R.
> >
> >
> > This probably going to show my vast ignorance of R in comparison to SPSS,
> but
> > is there a way to tell / set the significance level for the analysis?
>
> ?cor.test
>
> but beware that your observations are not independent, and will have
> inflated
> significance levels, so the test output really should not be used unless
> you
> can first show that there is no spatial autocorrelation in either variable.
> You
> could look at ?Geary in the raster package as a way of checking
> autocorrelation. If you are an ecologist, you could look at Fortin & Dale
> for
> background, and maybe the Numerical ecology with R useR! book from
> Springer.
> The Moran() and Geary() functions in raster don't give you a significance
> test
> for autocorrelation, though, you may need other approaches in spdep for
> that.
>
> Hope this helps,
>
> Roger
>
> >
> > cheers,
> > Rebecca
> >
> >
> >
> >
>
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