[STATSGRASS] Re: [GRASS5] r.moran

[Roger Bivand]

On Wed, 22 Mar 2006, Wolf Bergenheim wrote:

> On Wed, 22 Mar 2006, Roger Bivand wrote:
> 
> >>
> >> You might be right. But I guess it wouldn't work for vectors?
> >
> > No, vectors are fully supported - in fact a raster would be treated as
> > cell centre points. See the range of functions for building lists of
> > neighbours in the R spdep package. Are your vectors points or polygons?
> 
> Hey that is good to know. Now I even have a reason to join that list (;
> 
> I have a bunch of vector areas that I'd need to do Moran's I on. Thing is 
> that I'm not very comfortable with R, so I guess I'll need some help.
> 
> > What criteria for neighbours do you need?
> 
> My vectors are polygons, squares actually, with sides of 1 km. So I guess a 
> neighbour is one that shares a boundary. I guess I could easily convert 
> these to rasters, but since they are vectors I can connect an attribute 
> table to them. I have to calculate Moran's I on many attributes.
> 

OK. Do the squares cover a whole rectanglar region, or are there ragged 
edges, holes, etc? Are they now stored as GRASS vector - I guess yes? How 
many are there? What kind(s) of variables do you need to test for 
autocorrelation, categorical or continuous-valued?

There will be three steps:

1) get the data into R

2) build the neighbour representation, and

3) test

where variants of 1 & 2 will depend on how your data are represented now.

> > We can continue thread this on the STATGRASS list if you like.
> >
> 
> I'm not on that list (yet), so for now if we want (yes we do since this is 
> OT) to keep this away from here, I guess we could switch to the STATGRASS 
> list, plus me as Cc.
> 

I suggested the list (another is R-sig-geo) because other people there may 
have directly relevant experience, I hope that makes sense!

Roger

> --Wolf
> 
> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no