I don't know how exactly works that, but I will try. Thank you.
El sáb., 22 de jun. de 2019 a la(s) 22:17, Juan Pablo Carranza ( carranzaju...@gmail.com) escribió: > 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 >> > -- 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