On 24-Oct-10 11:30:57, Lorenzo Isella wrote: > Dear All, > I would like to plot a scalar (e.g. a temperature) on a non-rectangular > domain (or even better: I would simply like to be able to draw a > contour plot on an arbitrary 2D domain). I wonder if there is any > tool to achieve that with R. I did some online search in particular > on the list archives, found several queries similar to this one but > was not able to find any conclusive answer. > I am interested in the following 2 options > > (1) just read a file of the form > > x1 y1 z1 > x2 y2 x2 > ... ... ... > xn yn zn > > where the set of {xi} and {yi} are coordinates on an arbitrary domain > and {zi} are the values of the scalar for the corresponding {x,y} > coordinates. > (2) Sometimes the domain where I want to draw a contour plot is nothing > too fancy and the scalar itself is given by an analytical function. > Consider e.g. the case of a circle of radius R=pi/2 centered about the > origin and a function like > > z=f(x,y)=abs(cos(y)) > > NB: in this case a satisfactory solution could be to plot z on a > rectangular grid and then clip a circular region > To fix the ideas, the final result in this case (with a colorjet map) > should look like this > > http://dl.dropbox.com/u/5685598/scalar_plot.pdf > > Any suggestion is appreciated. > Many thanks > > Lorenzo
For your option (1), the fundamental issue is interpolation. There are many methods for this, with different proprties! An R Site Search on "interpolation" yields a lot of hits. One (which is fairly basic, but may suit your purposes) is the interpp() function in package akima: http://finzi.psych.upenn.edu/R/library/akima/html/interpp.html Hoping this helps, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Fax-to-email: +44 (0)870 094 0861 Date: 24-Oct-10 Time: 12:51:03 ------------------------------ XFMail ------------------------------ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.