I have a dataset of boundaries and centroids where sometimes centroids are missing because of digitizing errors. I tried to create new centroids using v.centroids, but that did not work (please see my message from May 12.)
Then I tried to use v.category with options type=area and option=add along with cat=9000, and that works. I get new centroids with the desired cat values (up from 9000). The rest of the columns for the new centroids show NULL. Funny thing about the new centroids: they show up when viewing the map in QGIS or when using d.vect, but they are not visible when listing the table using db.select. I don't understand that. Now, I need to transfer the category values of the new centroids to another existing column, but that doesn't work. Here are the commands I tried one at a time: v.db.update map=inputmap, column='myCol', query_column='cat', where="cat >= 9000" db.execute sql="UPDATE inputmap SET myCol = cat WHERE cat >= 9000") Both commands don't work as expected. The values in "myCol" for the new centroids stay NULL, no matter what. When I set another filter (for example, cat >1), they both work fine for those centroids that were existing from the beginning - but not for the new ones. I also tried to insert random integer values into "myCol", but this also works only for the old centroids. The new ones don't accept changes. At least it means we have no syntax error or something like that. Any ideas what's wrong? Why are the new cents not completely accepted? Thank you very much! best regards, Uwe
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