Message-ID: <F7884F17-0018-46D2-979B-AFC38DF92E38@ais-int.com>
Date: 2010-09-05T20:11:48Z
From: German Sanchez Hernandez
Subject: Complete neighbours
In-Reply-To: <alpine.LRH.2.00.1009051953590.28150@reclus.nhh.no>
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 escribi?:
> 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!
>> Germ?n S?nchez
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at 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.Bivand at nhh.no