Dear Roger (and list): Thank you for your response. The idea to complete the neighbourhood list is to try to "define" some regions using the features of their nearest regions.
I made a modification of union.nb function, once I've learned how to edit the nb objects. I'll take a look on the nblag_cumul function. Thanks and regards, German Sanchez El 05/09/2010, a las 21:14, Roger Bivand escribió: > On Fri, 3 Sep 2010, German Sanchez Hernandez wrote: > >> Dear list, >> >> I would like to complete my neighbour list in order to increase the number >> of neighbours of regions with less neighbours (links) than a certain number. >> The idea is to complete these links using knearneigh function. >> >> >> My try: >> >> nb <- poly2nb(map) >> # Compute distribution of linkage: >> distr <- as.data.frame(table(card(nb))) >> # Try to identify the "isolated" regions (equal or less than, for example, 3 >> neighbours >> minim <- 3 # It's a computed number >> isolated <- subset(nb, subset=card(nb) <= minim) >> # Get the "isolated" region IDs >> regions <- attr(unclass(isolated), 'region.id') >> # Modify nb using knearneigh ¿? > > For the edited version of nblag_cumul on R-forge on the spdep project, you'd > do something like: > > example(columbus) > table(card(col.gal.nb)) > k4 <- knn2nb(knearneigh(coordinates(columbus), 4)) > mod_nb <- nblag_cumul(list(col.gal.nb, k4)) > table(card(mod_nb)) > > but I'm not at all sure that this is a good idea. Most often observations > with few neighbours are on the edge of the data set, so there is a very good > reason for their apparent "isolation". > > Hope this helps, > > Roger > >> >> >> # Alternative 2: >> nbmat <- nb2mat(nb) >> # Modify nbmat ¿?, mat2listw, listw2nb >> >> >> # Alternative 3: >> listw <- nb2listw(nb) >> # Modify listw ¿?, listw2nb >> >> >> The question is: >> >> How to modify nb (or nbmat or listw) to increase the number of links of the >> "isolated" regions? >> >> Any idea? >> >> Thank you! >> Germán Sánchez >> _______________________________________________ >> R-sig-Geo mailing list >> R-sig-Geo@stat.math.ethz.ch >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> > > -- > Roger Bivand > Economic Geography Section, Department of Economics, Norwegian School of > Economics and Business Administration, Helleveien 30, N-5045 Bergen, > Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 > e-mail: roger.biv...@nhh.no _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
