Hi, Loading the grid and telling R that it is a grid can also be done by:
library(gstat) data(meuse.grid) gridded(meuse.grid) =~x+y # Now it is a SPixelDF # The former is shorthand for: # coordinates(meuse.grid) =~x+y # gridded(meuse.grid) = TRUE fullgrid(meuse.grid) = TRUE # Make it a SGridDF cheers, Paul Edzer Pebesma wrote: > Ingo Holz wrote: > >> Hi, >> >> this sounds like a stupid question, however: >> >> I have a SpatialGridDataFrame (SGDF) and want to cut a rectangular >> subregion from this SGDF to a new sub-region-SGDF. >> >> Is it possible to define a new bounding-box with two points and cut the >> subregion out of the SGDF? >> >> Ingo >> >> _______________________________________________ >> R-sig-Geo mailing list >> [email protected] >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> >> > > data(meuse.grid) > > coordinates(meuse.grid)=~x+y > > meuse.grid=as(meuse.grid, "SpatialGridDataFrame") > Error in as(meuse.grid, "SpatialGridDataFrame") : > no method or default for coercing "SpatialPointsDataFrame" to > "SpatialGridDataFrame" > # this surprised me, but the following does work: > > meuse.grid=as(meuse.grid, "SpatialPixelsDataFrame") > > meuse.grid=as(meuse.grid, "SpatialGridDataFrame") > > image(meuse.grid[40:60,20:50,1]) > > # meaning the first index selects rows (top to bottom), and the second > columns; the third attribute > > > bbox(meuse.grid[40:60,20:50,1]) > min max > x 179200 180440 > y 331360 332200 > > x1 = bbox(meuse.grid[40:60,20:50,1])[1,1] > > x2 = bbox(meuse.grid[40:60,20:50,1])[1,2] > > y1 = bbox(meuse.grid[40:60,20:50,1])[2,1] > > y2 = bbox(meuse.grid[40:60,20:50,1])[2,2] > > p = Polygon(cbind(c(x1,x2,x2,x1,x1),c(y1,y1,y2,y2,y1))) > > sps = SpatialPolygons(list(Polygons(list(p),"bbox"))) > > meuse.grid=as(meuse.grid,"SpatialPixelsDataFrame") > > image(meuse.grid[!is.na(overlay(meuse.grid,sps)),1]) > > # this second form needs the grid represented as pixels, as the overlay > considers each grid cell, and retuns a vector the length of the number > of pixels. The image should be identical to the former. > -- > Edzer > > _______________________________________________ > R-sig-Geo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Drs. Paul Hiemstra Department of Physical Geography Faculty of Geosciences University of Utrecht Heidelberglaan 2 P.O. Box 80.115 3508 TC Utrecht Phone: +31302535773 Fax: +31302531145 http://intamap.geo.uu.nl/~paul _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
