On Thursday 06 March 2008, Thomas Adams wrote: > Dylan, > > I think a solution using GRASS can be found on pages 110-111 of "Open > Source GIS: A GRASS GIS Approach", 3rd Ed. The same material is covered > in the 2nd Ed. as well, where you use r.mapcalc to combine two rasters > and judicious use of MASKs; a conditional statement in r.mapcalc is the > key. > > Regards, > Tom
Hi Tom, Thanks for the suggestion. This works, but we were hoping to make the plot in R-- as the PDF output is hard to match with GRASS alone. I suppose I will just have to try using two rasters with spplot() and see what happens. Cheers, Dylan > Dylan Beaudette wrote: > > On Tuesday 04 March 2008, Edzer Pebesma wrote: > >> I find it hard to imagine how you want to plot two raster files on top > >> of each other. Do you want some form of transparency? If it is just one > >> overlaying the other, you could use overlay to find out which cells in > >> raster 1 to replace with those in raster 2 before plotting. > >> -- > >> Edzer > > > > Hi Edzer, > > > > I generally agree that plotting one raster file "over" another raster > > file would be of little use. In this case, one of the raster files (the > > interesting one) has been masked with nodata, such that it only really > > covers about 30% of the region of interest. The other raster is just > > contextual data, and thus would be useful to plot "behind" the first > > raster. > > > > Ideas? > > > > Dylan > > > >> Dylan Beaudette wrote: > >>> Hi, > >>> > >>> Is it possible to plot two raster images using spplot() in a manner > >>> similar to: > >>> > >>> pts <- list("sp.points", points_file, pch = 4, col = "black", cex=0.5) > >>> spplot(raster_file, zcol="elev.pred", sp.layout=list(pts)) > >>> > >>> Note that one of the raster images is an aerial photo, used only for > >>> context, while the second one is one with interesting z-values. The > >>> second raster is masked and thus does not cover the entire region. > >>> > >>> Thanks, > >>> > >>> Dylan -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo