[R-sig-Geo] Producing a conditional adjacency matrix

[Roger Bivand]

On Mon, 30 Sep 2019, Rhys Dubin wrote:

> Hi all,
>
> I have a question regarding matrices (produced using poy2nb in spdep).
>
> I’m trying to produce an adjacency matrix from a GIS Polygon shapefile 
> with about 500 individual polygons (queen or rook — it doesn’t really 
> matter for now), but conditional on the value of the parent polygon.
>
> For instance, if a polygon had an arbitrary value of 1, I want to return 
> a list of all neighboring polygons that have a value of 2 or 3 (ie. ≠ 
> 1). The same would go for a polygon with a value of 2 (ie. return all 
> neighbors with a value of ≠ 2).
>
> Is there a solution to this issue built into spdep, do I need to use a 
> different package, or is it possible to accomplish this with a 
> subsetting command?

No built-in solution, but to make progress a clear, reproducible example 
is essential, otherwise we're guessing what you want. For example, add a 
doctored variable to the eire or columbus data sets to show your needs. Do 
you want a glist including (1) all neighbours j with a value of x not 
equal to x[i], and excluding (0) all with x[j] == x[i]?

Roger

>
> Thanks!
>
> Rhys
>
>
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-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: Roger.Bivand using nhh.no
https://orcid.org/0000-0003-2392-6140
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