HI, thank you for that. I had come across a while ago a presentation outlining the ideas for such a function but can't remember who or where.
Thanks again, Tim ----- Original Message ----- From: Duncan Murdoch <[email protected]> Date: Tuesday, May 12, 2009 4:26 pm Subject: Re: [R] Response surface plot To: Tim Carnus <[email protected]> Cc: [email protected] > On 5/12/2009 8:43 AM, Tim Carnus wrote: > > Dear List, > > I am trying to plot a similar graph to > attached from minitab manual in R. > > I have a response Y and three components > which systematically vary in their > > proportions. I have found in R > methods/packages to plot ternary plots (eg. > > plotrix) but nothing which can extend it to > response surface in 3-D. > > Any help appreciated, > > I'm not aware of anyone who has done this. The way to do > the surface in > rgl would be to construct a mesh of triangles using tmesh3d, and > set the > color of each vertex as part of the material argument. It's a > little > tricky to get the colors right when they vary by vertex, but the > code > below gives an example. > > I would construct the mesh by starting with one triangle and > calling > subdivision3d, but you may want more control over them. > > For example: > > library(rgl) > > # First create a flat triangle and subdivide it > triangle <- c(0,0,0,1, 1,0,0,1, 0.5, sqrt(3)/2, 0, 1) > mesh <- tmesh3d( triangle, 1:3, homogeneous=TRUE) > mesh <- subdivision3d(mesh, 4, deform=FALSE, normalize=TRUE) > > # Now get the x and y coordinates and compute the surface height > x <- with(mesh, vb[1,]) > y <- with(mesh, vb[2,]) > z <- x^2 + y^2 > mesh$vb[3,] <- z > > # Now assign colors according to the height; remember that the > # colors need to be in the order of mesh$it, not vertex order. > > vcolors <- rainbow(100)[99*z+1] > tricolors <- vcolors[mesh$it] > mesh$material = list(color=tricolors) > > # Now draw the surface, and a rudimentary frame behind it. > > shade3d(mesh) > triangles3d(matrix(triangle, byrow=TRUE, ncol=4), col="white") > quads3d(matrix(c(1,0.5,0.5,1, 0,sqrt(3)/2, sqrt(3)/2,0, > 0,0,1,1), > ncol=3), col="white") > bg3d("gray") > > Duncan Murdoch [[alternative HTML version deleted]]
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