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============================================================================================================================================================= On 13/12/2010 10:13 AM, Uwe Wolfram wrote: Dear R-Users, I am currently trying to fit a tensorial function in its principal coorinate system. The function is given by: 1~(x1^2 + x2^2 + x3^2 - chi0*(x1*x2 + x1*x3 + x2*x3))/eps0^2 + (x1 + x2 + x3)/xi0 Where eps0 = 0.0066, chi0 = -0.66 and xi0 = 0.011 are obtained from experimental data using nls().I am able to plot the experimental points that delivered the parameters of the function. For my thesis, however, I need to overlay the fitted surface. So far I am using the following code which wonderfully plots the experimental points in 3D: =================================================================== # from demo(bivar) require(rgl) require(misc3d) require(MASS); # New window open3d() # clear scene: clear3d("all") # setup env. That is, background, light and so on: bg3d(color="#887777") light3d() # spheres at points in principal strain space #spheres3d(e1,e2,e3,radius=0.00025,color="#CCCCFF") # draws points alternatively plot3d(e1,e2,e3, col="#CCCCFF") =================================================================== According to the examples on http://rgl.neoscientists.org/gallery.shtml I tried to overlay the point plot using surface3d. However, these were only functions of type y ~f(x1, x2). I think that the surface could be plotted if I could provide the gridpoints correctly. Using xyz.coords(1~(x1^2 + x2^2 + x3^2 - chi0*(x1*x2 + x1*x3 + x2*x3))/eps0^2 + (x1 + x2 + x3)/xi0, y = NULL, z = NULL) did unfortunately not solve the problem. Is there any function that can generate the surface for the given function such as ContourPlot3D in Mathematica. See ?misc3d::contour3d ______________________________________________ R-h ... @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.