Hi GRASS users, I am working on a polygon map of France that shows the single areas belonging to a specific postal code. I want to extract for each area the centroid (using v.extract), transform it to a point map (using v.type) and finally add the X and Y coordinates to the attribute table for each postal code region.
However, now I have the problem that some "postal code areas" have more than one centroid, i.e. two or more closeby but not connected polygons belong the same postal region and share a common category and entry in the attribute table. So for these cases I get two or more points (sharing the same cat) and of course I cannot calculate a single XY pair for that postal code region. Consequently, I need to find a method to get centroids of all the areas sharing a common cat or I need to calculate the mean position of points afterwards (using v.centerpoint). As far as I understood v.centerpoint all points are used to calculate a mean point but not stratified for points sharing the same cat!? FYI: I have around 2000 postal code areas of which 200 consists of more than a single polygon. Any suggestions? /Johannes
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