Hi all,
Many thanks to Roger for trying to replicate my problem with nblag_cumul! You are correct in assuming that I am working with a GISCO map on multiple levels, i.e. a combination of Nuts 1 and Nuts 2 regions. However, the regions are distinct and not overlapping, so I presumed that this should not constitute a problem. You can inspect my regional classification in the directory where I stored my shapefile: ftp://ftp.uibk.ac.at/private/c43227_20101117_a7cbdd66 <ftp://ftp.uibk.ac.at/private/c43227_20101117_a7cbdd66> Quick reminder: My problem lies in creating a second order queen matrix with nblag_cumul when one region does not have any second order regions and nblag_cumul produces a row of zeros for all first order neighbors of this region. I was able to circumvent the problem by computing the path matrix (multiplication of first order queen with itself) and merging the two matrices making sure that the diagonal consists of zeros and all second order neighbors are indicated with ones. That should do the trick, my whole code is the following: # Construction of second ord. queen mat with nblag (nb2listw command fails because of empty neighbor set) shapef <- readShapeSpatial("Europe_N1_N2") queen.nb <- poly2nb(shapef) second.order.lag <- nblag(queen.nb, 2) queen2.nb <- nblag_cumul(second.order.lag) queen2.lw <- nb2listw(queen2.nb, style ="W") # Alternative solution based on path matrix queen.mat <- nb2mat(queen.nb, style = "B") queen2.temp1 <- queen.mat %*% queen.mat vec.queen2 <- diag(queen2.temp1) diag.queen2 <- diag(vec.queen2) queen2.temp2 <- queen.mat + queen2.temp1 queen2.temp3 <- queen2.temp2 - diag.queen2 queen2.temp4 <- as.numeric(queen2.temp3 != 0) queen2.mat <- matrix(data = queen2.temp4, nrow = 118, ncol = 118) queen2.rs.mat <- solve(diag(rowSums(queen2.mat)))%*% queen2.mat queen2.lw <- mat2listw(queen2.rs.mat) In addition, another problem has surfaced when computing centroids. I presume that centroids for the polygons in my dataset can be computed with the coordinates() command in R: # computation centroids coord <- coordinates(shapef) coord For a comparison I also computed the centroids in ArcGis (generation of x and y columns in the attribute table, right click on x and y, calculate geometry, property: x/y coordinate of centroid). These coordinates are indicated in the shapefile and in the excel output file of the attribute table (also stored in the zip file). In this output file the values for x/y coordinates of ArcGis and R centroids are compared. Most are pretty much identical, for a few there are some discrepancies (of up to 60 km). My questions now are the following: * Presuming my alternative solution for the second order queen is correct, is there a more efficient way to compute this matrix (maybe based on nblag)? * What could be a possible explanation for the discrepancies in the computation of regional centroids for ArcGis and R? Sorry for this lengthy post, any suggestions and explanations would be greatly appreciated! Best regards, Christoph Dr. Christoph Hauser University of Innsbruck Department of Economic s Universitaetsstrasse 15 6020 Innsbruck Tel.: 0043 512 507 7354 Fax: 0043 512 507 2980 [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
