Rolando, thanks for clarify. "gdistance" may give you what you are looking for. Another option is the package "osrm", for calculate distances using Open Street Maps routes. Once you calculate a dataframe with the distances of every pair of locations, you could make ones and ceros with a simple ifelse. Then you could standarize by row. That will be your lw matrix. Here is some help:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://cran.r-project.org/web/packages/gdistance/vignettes/gdistance1.pdf&ved=2ahUKEwim8u3P-f7iAhV5GLkGHbUKBCUQFjAAegQIAxAB&usg=AOvVaw2EjdceAFDJB9Qet-EBEDAn&cshid=1561271237676 Juan Pablo Carranza Mgter. en Administración Pública Lic. en Economía El dom., 23 de jun. de 2019 3:02 a. m., Rolando Valdez <rvald...@gmail.com> escribió: > I apologize for the lack of clarity. > > Let me try again: > > The SWM captures the spatial structure among territories. In the case of a > matrix based on distance, you define a distance-threshold, say 50 km, and > every territory under that distance is considered as neighbor, in the > matrix, those territories considered neighbors take the value 1, and 0 > otherwise (territories beyond 50 km). This is what 'dnearneigh' function > does. > > Then, I want to define a distance-threshold, say 50 km by road (not > euclidean) and every territory under that distance (by road) be considered > as neighbor. > > El sáb., 22 de jun. de 2019 a la(s) 21:15, Rolf Turner ( > r.tur...@auckland.ac.nz) escribió: > > > On 23/06/19 3:30 PM, Rolando Valdez wrote: > > > Sorry again. > > > > > > A Spatial Weight Matrix (swm) is an object used in spatial econometrics > > > to characterize the spatial structure among territories. It is an > > > element nxn where n is the number of territorial units (counties, > > > districts, states, cities, regions) in the sample and it could be based > > > on contiguity or distance. Usually, you can create a swm based on > > > distance using 'dnearneigh' from spdep and then convert to a listw > > > through 'nb2listw'. The problem is that the matrix that you generate > > > trough 'dnearneigh'computes the euclidean distance among centroids of > > > polygons. This is where I spot my issue, I need to compute the swm > using > > > the road distance instead of euclidean distance computed through > > > 'dnearneigh'. I do have a shapefile with poligons (counties) and > another > > > shapefile with lines (roads). > > > > OK. It's getting a *bit* clearer .... You are interested in "road > > distances" between counties. I'm still not entirely sure what this > > means. Is it the *minimum* distance by road from one county to another? > > In which case, if two counties are contiguous (adjacent) and there is a > > road crossing the border between the two, is the distance between the > > counties equal to zero? (This doesn't seem like it would be > > satisfactory ....) > > > > Yes, actually it is possible that two counties were connected by more > than > one road, however it's not a big deal. If I define a distance of 50 km, it > doesn't matter how many times two counties are connected, I just need that > they are at 50 km trough, at least, one road. > > > If this is not the case, then what *is* the case? Perhaps you want > > distances between the *centroids* of the counties. What then do you > > mean by road distance when the centroids do not lie on a road? > > > > This is a big challenge, I'm still working on it. > > > > > You apparently need to deal with counties in which there are no roads at > > all. To handle this you have to define what *you* mean by the distance > > by road from county A to county B when there are no roads at all in > > county B. Perhaps infinity would be the appropriate distance, but *I* > > don't know; you have to make the call. > > > > If two counties are not connected through a road, they could not be > neighbors. In this case, it would correspond to a value 0 in the matrix. > > > > > Previously you indicated that you needed to know (pairwise) road > > distances between specified points in a given set, and I showed you how > > to obtain those using pairdist(), from spatstat. Now it seems that you > > want something rather different, and it's still not clear what. > > > > In a sense is the same, but you said so properly, We have different > research fields. > > > > You need to get *your* thoughts clear; make some definitions and > > specifications, and decide what you really want or need. > > > > I got it. > > > > > It seems that you are expecting R to magically do your thinking for you; > > it won't! > > > > No, I'm not expecting that. > > > cheers, > > > > Rolf > > > > > El sáb., 22 de jun. de 2019 a la(s) 20:00, Rolf Turner > > > (r.tur...@auckland.ac.nz <mailto:r.tur...@auckland.ac.nz>) escribió: > > > > > > > > > On 23/06/19 2:38 PM, Rolando Valdez wrote: > > > > > > > I am sorry, I was not clear enough. My goal is to calculate a > > > spatial > > > > weight matrix (nxn) across counties but, instead of euclidean > > > distance, > > > > to use road distance. > > > > > > I'm afraid I still don't understand. To put it mildly. You > > presumably > > > have a clear idea of what you are trying to, but those of us who > are > > > not > > > involved in your research have no such idea. We (or at least I) > > > haven't > > > a clue as to what you are talking about. > > > > > > What do you mean by "spatial weight"? What are these weights used > > for? > > > What is n? How are the counties involved? Is n the number of > > > counties? > > > Are you interested in the road distance (minimum road distance?) > > > between > > > pairs of counties? > > > > > > Please explain *clearly* and do not expect those who are trying to > > help > > > you to be mind-readers!!! > > > > > > cheers, > > > > > > Rolf > > > > > > > > > > > El sáb., 22 de jun. de 2019 a la(s) 19:28, Rolf Turner > > > > (r.tur...@auckland.ac.nz <mailto:r.tur...@auckland.ac.nz> > > > <mailto:r.tur...@auckland.ac.nz <mailto:r.tur...@auckland.ac.nz>>) > > > escribió: > > > > > > > > > > > > On 23/06/19 1:17 PM, Rolando Valdez wrote: > > > > > > > > > Thank you for your answer. > > > > > > > > > > I have a shapefile with, say, counties, and I got another > > > > shapefile with > > > > > the roads. ¿What if a county does not intersect any road? > > > > > > > > I am sorry, but it is not at all clear to me just what the > > > problem is. > > > > How do the counties come into the picture? You said you > > > wanted to get > > > > the road distance between points on the roads. What have > the > > > counties > > > > got to do with this? > > > > > > > > Can you perhaps provide a reproducible example? > > > > > > > > cheers, > > > > > > > > Rolf > > > > > > > > > > > > > > El jue., 20 de jun. de 2019 a la(s) 19:08, Rolf Turner > > > > > (r.tur...@auckland.ac.nz <mailto:r.tur...@auckland.ac.nz > > > > > <mailto:r.tur...@auckland.ac.nz <mailto:r.tur...@auckland.ac.nz>> > > > > <mailto:r.tur...@auckland.ac.nz > > > <mailto:r.tur...@auckland.ac.nz> <mailto:r.tur...@auckland.ac.nz > > > <mailto:r.tur...@auckland.ac.nz>>>) > > > > escribió: > > > > > > > > > > > > > > > On 21/06/19 12:26 PM, Rolando Valdez wrote: > > > > > > > > > > > Dear community, > > > > > > > > > > > > Is there any way to create a spatial weight matrix > > > based > > > > on road > > > > > distance? > > > > > > I am trying to use the road distance between two > > points > > > > instead of > > > > > > euclidean distance. > > > > > > > > > > > > I've seen that there is a package named osrm. Can > > > anyone give > > > > > some advice? > > > > > > > > > > I don't know anything about "osrm". Calculating > "road > > > distances" > > > > > can be > > > > > done in the spatstat package reasonably easily, if > you > > > take > > > > the trouble > > > > > to represent your collection of roads as a "linnet" > > > object. > > > > > > > > > > Given that you have done so, suppose that your linnet > > > object > > > > is "L" and > > > > > that you have vectors "x" and "y" specifying the > > > points on L > > > > (i.e. on > > > > > your roads) between which you want to know the > > distances. > > > > > > > > > > Do: > > > > > > > > > > X <- lpp(data.frame(x=x,y=y),L) > > > > > dMat <- pairdist(X) > > > > > > > > > > The object "dMat" is a (symmetric) square matrix; > > > dMat[i,j] > > > > is the > > > > > distance between point i and point j. (Of course the > > > > diagonal entries > > > > > are all 0.) > > > > > > > > > > If your collection of roads is specified by means of > a > > > shapefile, > > > > > vignette("shapefiles") will tell you how to turn this > > > > collection into a > > > > > "psp" ("planar segment pattern") object; the function > > > (method) > > > > > as.linnet.psp() can then be used to turn the "psp" > > > object into a > > > > > "linnet" object. > > > > > > > > > > HTH > > > > > -- > Rol~ > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo