subsetting a spatial polygons
crop doesn't select it actually cuts on the boundary, for simple shapes I use coordinates (for centroids in easy matrix) and select with [ using tests on x and y. Cheers, Mike
On Wed, Sep 12, 2018, 15:29 Tim Appelhans <tim.appelhans at gmail.com> wrote:
Antonio, I am not sure why you think that your solution is not very elegant. In case you want to have more visual control over the subsetting, you could try mapedit: library(mapedit) myselection = selectFeatures(polys, mode = "draw") which will let you draw a e.g. rectangle and only return those features that intersect it. Best Tim On 09/12/2018 04:18 AM, Antonio Silva wrote:
Dear list users I have a SpatialPolygons with several squares. How to subset it to have only the squares between given latitudes and longitudes? In the example library(sp) library(raster) grd <-
GridTopology(cellcentre.offset=c(-47.75,-25.416667),cellsize=c(10/60,10/60),cells.dim=c(23,12))
polys <- as.SpatialPolygons.GridTopology(grd)
proj4string(polys) <- CRS("+proj=longlat +datum=WGS84")
plot(polys,axes=T)
How to select only the squares, let's say, between 24-25?S and 45-46?W?
The farthest I went was:
e <- extent(-45.9,-45.1,-24.9,-24.1) # which is not very elegant
mask <- crop(polys,e)
polys2 <- polys[mask,]
plot(polys2,add=T,col="green")
Thanks a lot. Best regards
_______________________________________________ R-sig-Geo mailing list R-sig-Geo at r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Dr. Michael Sumner Software and Database Engineer Australian Antarctic Division 203 Channel Highway Kingston Tasmania 7050 Australia [[alternative HTML version deleted]]