[R-sig-Geo] Errors while creating a neighbourhood matrix using poly2nb

[Oscar Breugelmans]

Hi everybody,

I am trying to create a neigbourhood matrix based on a shapefile of postal
code areas that was created in ArcMap. Normally this works fine using the
'readShapePoly' and 'poly2nb' commands. However, the postal code areas
change over the years or are made up of 2 or mory polygons because they are
situated on both sides of a large waterway. I correct these difficulties by
merging postal code areas in ArcMap, so that I end up with a shapefile in
which each postal code area is represented by just 1 polygon with an unique
area ID.
I again import the updated shapefile in R using readShapePoly. But then the
problems start. When I create a neighbourhood matrix using poly2nb, the
areas that have been merged behave very strange: they don't recognize their
neighbours. Sometimes they recognize none, sometimes a few.
When I couldn't find a solution I tried to create the nb using GeoDa. This
gave exactly the same problems. Then I turned to GeoBugs and - surprise -
the nb was created without any problems.

Does anyone recognize these problems or has a solution for me?

Thanks,
Oscar
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