> > In the trellis panel functions, or in the direct plot/image/lines etc > > functions, you plot in data coordinates. The main thing that the plot > > and spplot methods in package sp control is the aspect ratio. How else > > do data coordinates differ from geographical coordinates when it comes > > to plotting? > > Exactly. In fact I think that a grid panel might make it possible to > insert an image backdrop behind spplot(), which was the original question > from Dylan - it would make a nice student project in visualisation. > Something like an sp.image() for sp.layout=, but using its own palette and > being painted over by the "real" data.
Another approach would be to develop a better interface between spatial data and ggplot2, which provides much better support for layer compositing (and in general for modifying a plot after you have created it). There are some simple examples at http://had.co.nz/ggplot2/geom_polygon.html and http://had.co.nz/ggplot2/coord_map.html, but I don't know enough about the problems of spatial data to be able to do it all myself. Hadley -- http://had.co.nz/ _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
