2010/8/26 Michał Kwieciński <jamesbo...@gmail.com>: > 2010/8/26 Roger Bivand <roger.biv...@nhh.no>: >> On Thu, 26 Aug 2010, Michał Kwieciński wrote: >> >>> 2010/8/26 Roger Bivand <roger.biv...@nhh.no>: >>>> >>>> On Thu, 26 Aug 2010, Michał Kwieciński wrote: >>>> >>>>> Hi all, >>>>> >>>>> I am just about to finish my thesis. The spatial model I want to use >>>>> there is an extension of some work I did back in April. I used R 2.9.2 >>>>> then and in order to include 3 additional administrative areas for >>>>> Poland, I edited the shp files (the borders aren't perfectly aligned). >>>>> Then in R I created the nb class object and edited it with edit.nb >>>>> adding three new connections. Everything worked perfect, I had no >>>>> regions with no links and I generated weight matrices with no >>>>> problems. >>>>> >>>>> However, I'd been doing exactly the same thing entire night in R 2.11 >>>>> and it did not work (I use the same code I did 4 months ago) and I >>>>> have no idea what is the reason for it. I've been looking for some >>>>> other way to do it, I tried nb2mat and editing the matrix, but I >>>>> surrendered having no idea where and what values I should use. >>>>> >>>>> Before editing nb object R claims that regions 377 and 378 have no >>>>> links. However in edit.nb the 378 and 379 are visible as having no >>>>> links (378 and 379 are cities added on top of bigger shapes, whereas >>>>> 377 was just split from a bigger shape into two smaller ones and only >>>>> the link between these two parts is missing). I connect the circles, >>>>> quit and in the new object there are some new links - the overall >>>>> number has increased - but 377 and 378 are still listed as having no >>>>> links. Editing nb again shows the links, so they have been saved for >>>>> sure. >>>>> >>>>> I am not an advanced R user and most of my code was based on my >>>>> professor's book. However, I think I have spent enough time with >>>>> spatial models and those matrices in order to call this problem really >>>>> weird. Especially since it worked perfectly last time... >>>>> >>>>> I can attach shp files and my code if it will be of any help in order >>>>> to properly investigate this problem. I would really appreciate some >>>>> help, I need to finish the project over the weekend. >>>> >>>> Maybe you are using the wrong indices, as FIDs are 0-base but nb objects >>>> are >>>> 1-base. So you may be editing the wrong ones. If this doesn't resolve the >>>> problem, zip the shapefile and post a link to it, don't attach the >>>> shapefile, as it would be sent to 1700 people. >>> >>> >>> I must admit I did not understand your hint (I do not know what "base" >>> is, assuming FID is Field ID - header in shp file). How is it possible >>> I edited some other layer of information by function edit.nb? Could >>> you please clarify what should I do to check it? >> >> Google "0-based" gets you to Wikipedia: >> >> "0 (zero-based indexing) >> The first element of the array is indexed by subscript of 0. >> 1 (one-based indexing) >> The first element of the array is indexed by subscript of 1." >> >> So the FIDs in the shapefile are 0, ..., (n-1), and identify the >> observations, so are set in the region.id attribute of the nb object. Then >> if print(nb) says that "377" and "378" have no neighbours, and the region.id >> values are from the shapefile: >> >> which(card(nb) == 0) >> >> will likely say 378 379, and >> >> attr(nb, "region.id")[which(card(nb) == 0)] >> >> will say "377" "378". >> >> The indices used internally in edit.nb are the 1-based indices. They >> probably should be the ones stored in the region.id attribute, but this >> would involve an extra level of indexing. If you don't understand, put the >> shapefile on a website and post the link. >> > Ok, now I understand. This is true in my case - it explains why I see > different numbers in listing of "no-links regions" and on the map in > edit.nb. That brings me only to the main question: why, even after > connecting the nodes (and verifying they are connected with plot.nb), > the print(nb) still says that those two regions remain unconnected? > > http://home.elka.pw.edu.pl/~mkwiecin/edit.nb-problem.rar > > I uploaded here the code I use, maps and two screens explaining where > to look for the missing links in question.
Ok, I did what I should have done at the very beginning (I even gave myself a hint to do that on the beginning of my first message...). Anyway, installed R 2.9.2 again and it appears to be working correctly - no missing links after edit.nb(). I do not know what author of this ( https://stat.ethz.ch/pipermail/r-sig-geo/2010-July/008908.html ) message meant, but I suppose he had the same problem. I will continue working on 2.9.2 version, so by now I am grateful for your help Roger, but I don't think it is necessary to investigate in hurry why edit.nb does not work in 2.11. Thank you again, Michal _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
