Hi all! I don't have the specific answer, but I don't appreciate academic bullying either. So... here is a way you could take. Go to qgis, calculate road distances by network analysis and then add it to your dataframe. Use this new variable to weigth the matrix. I hope this serves, and I hope Rolf solves what ever is bothering *him*. Cheers
Juan Pablo Carranza Mgter. en Administración Pública Lic. en Economía El dom., 23 de jun. de 2019 1:16 a. m., 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 ....) > > 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? > > 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. > > 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. > > You need to get *your* thoughts clear; make some definitions and > specifications, and decide what you really want or need. > > It seems that you are expecting R to magically do your thinking for you; > it won't! > > 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 > > _______________________________________________ > 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