contour labelling [was "Re: [R] image ()"]
On Fri, 4 Dec 1998, Thomas Lumley wrote:
On Thu, 3 Dec 1998, Bill Simpson wrote:
include upgrading contour, image, persp etc. In addition I hope that he will also add some mapping facilities along the lines of GMT (using their shoreline database). Now would be a good time to make suggestions about desirable features.
OK this may be a long shot. I often have to make a plot of like this: the heights (z) of trees in a forest (whose locations are unif rand x,y) are recorded. Now we make a 3D shaded surface plot of the (x,y,z) data. A triangular mesh is made by finding the Delaunay triangulation (nearest neighbours are connected). I am not talking about doing some form of interpolation (hence forcing the data onto a regular grid).
There is GPLed Delaunay triangulation code in Java (including a fast approximate algorithm) as part of Visad (http://www.ssec.wisc.edu/~billh/visad.html). There is an old C implementation which may well have the same algorithms.
There is Delaunay code in the R package tripack, and, implicitly, in package akima which may well be helpful: if I understand Bill correctly he wants to put a plane on each triangle to get a surface (which is interpolation) and Akima was more sophisticated and used quintics to achieve a smooth interpolated surface. We may be missing the crux here: was it to have a means of displaying such surfaces?
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._