Getting better contour plots with S and GCVPACK

We show how to obtain esthetically pleasing contour plots using New S and GCVPACK. With these codes, thin plate splines can easily be used to interpolate “exact” data, and to produce smoothly varying contour plots, with none of the jagged corners that plague many other interpolation methods. It is noted that GCVPACK can also be used to interpolate data on the sphere and in Euclidean three space. We observe that a larger class of global interpolation methods (including the thin plate spline) have a Bayesian interpretation, and GCVPACK can be used to compute them.