[R-sig-Geo] Creating new neighbour's list for aggregated regions and writing to shapefile

[Roger Bivand]

On Sat, 27 Sep 2008, Roberto Patuelli wrote:

> Hi All,
>
> I want to aggregate my NUTS-3 regions in bigger ones, for which, of 
> course, I have corresponding codes. I have two main problems:
>
> 1) In terms of map visualization, I used unionSpatialPolygons(),
>    starting from my original shape file. At this point I would like to
>    write the resulting object out to a shape file by writePolyShape(),
>    but R gives me the following answer:  class(x) ==
>    "SpatialPolygonsDataFrame" is not TRUE

You have created a new SpatialPolygons object, say x, but shapefiles also 
need attribute data. As an absolute minimum, do

IDs <- sapply(slot(x, "polygons"), function(i) slot(i, "ID"))
# to retrieve the new IDs
df <- data.frame(y=rep(1, length(IDs)), row.names=IDs)
xx <- SpatialPolygonsDataFrame(x, data=df)
writePolyShape(xx, "filename")

>
> 2) In order to use spatial econometric techniques, I need to obtain a
>    new neighbours list. Because of islands problems that have already
>    been solved, rather than creating a new spatial weights matrix, I
>    would like to obtain this by aggregating the one based on the
>    original regions, or by aggregating directly the neighbour's set (a
>    listw object for example), if possible.

This looks like a new function for spdep, somewhat like the reverse of 
nb2blocknb(). If you could provide me with an example off-list, I'll see 
what can be done.

Roger

>
> Can anyone help on these two problems?
>
> Thanks and best regards,
> Roberto Patuelli
>
>
>
> ********************
> Roberto Patuelli, Ph.D.
> Post-doc researcher
> Institute for Economic Research (IRE)
> University of Lugano (USI)
> via Maderno 24, CP 4361
> CH-6904 Lugano
> Switzerland
> Phone: +41-(0)58-666-4166
> Email: roberto.patuelli at lu.unisi.ch
> ********************
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-- 
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