Thank you Edzer, the solution with the interpolation was exactly what I was searching for.
best regards, stefan On Thu, Sep 16, 2010 at 09:57:01PM +0200, Edzer Pebesma wrote: > Stefan, your data are definitely not on a grid, so either you transform > them back to the grid on which they were, or alternatively you could > interpolate them to a new grid, e.g. by > > library(sp) > link <- "http://z107.de/uni/example16092010.RData"; > load(url(link)) > coordinates(data) <- c("lon","lat") > diff(sort(unique(coordinates(data)[,2]))) > diff(sort(unique(coordinates(data)[,2]))) > bb = bbox(data) > gt = GridTopology(c(bb[1,1],bb[2,1]), c(.18,.18), round(c(diff(bb[1,]), > diff(bb[2,]))/.18) + 1) > plot(data) > plot(SpatialGrid(gt),col='red',add=T) > sp = SpatialGrid(gt) > fullgrid(sp)=F > spx = SpatialPixelsDataFrame(sp, data.frame(x = rep(NA, 44*16))) > library(gstat) > #proj4string(data)="+proj=longlat" > #proj4string(spx)="+proj=longlat" > sp2 = idw(Therm.Eignung~1,data,spx) > image(sp2,axes=T) > spplot(sp2[1], col.regions=bpy.colors()) > > > On 09/16/2010 08:31 PM, Stefan Muthers wrote: > > Hello, > > > > this is probably a beginners question, but I found no solution on the > > web. > > > > If am using data from a climate model with the cell positions given in > > geographic coordinates. Unfortunatly the distance between the cells is > > uneven (due to runding errors and maybe the projection) and the > > "gridded" command fails to determine the correct cell size. > > > > > > Consider the following example: > > > > > > library(fields) > > library(sp) > > > > link <- "http://z107.de/uni/example16092010.RData"; > > load(url(link)) > > > > coordinates(data) <- c("lon","lat") > > gridded(data) <- TRUE > > # Warnmeldungen: > > #1: In points2grid(points, tolerance, round, fuzz.tol) : > > # grid has empty column/rows in dimension 1 > > #2: In points2grid(points, tolerance, round, fuzz.tol) : > > # grid has empty column/rows in dimension 2 > > > > data_sp <- as(data, "SpatialGridDataFrame") > > g_plot <- as.image.SpatialGridDataFrame(data_sp["Therm.Eignung"]) > > image.plot(g_plot) > > > > > > > > The resulting map contains only small stripes and much empty space. > > summary(data) reveals, that the cellsize if much to small (cell should > > be quadratic with a cellsize of ~ .16) and to many cells were found in > > the y-direction. > > > > When I replace the lat and lon values with simple x and y coordinates, > > everything works fine, but then it is not possible to overlay a shape > > file, that displays the country borders. > > > > Any ideas, why the cellsize-estimation is so different from the real > > value and what I can do, to create a raster map with this data? > > > > > > thank you and best regards, > > > > stefan > > > > _______________________________________________ > > R-sig-Geo mailing list > > R-sig-Geo@stat.math.ethz.ch > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > -- > Edzer Pebesma > Institute for Geoinformatics (ifgi), University of Münster > Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251 > 8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de > http://www.52north.org/geostatistics e.pebe...@wwu.de > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
