Duncan, thanks for the tip! I actually saw this 2D function but had no idea how to use it in 3D. Works great.
Remko ------------------------------------------------- Remko Duursma Research Lecturer Centre for Plants and the Environment University of Western Sydney Hawkesbury Campus Richmond NSW 2753 Dept of Biological Science Macquarie University North Ryde NSW 2109 Australia Mobile: +61 (0)422 096908 www.remkoduursma.com On Mon, May 10, 2010 at 9:24 AM, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 09/05/2010 6:41 PM, Remko Duursma wrote: >> >> Dear R-helpers, an rgl-ers in particular, >> >> >> what is the easiest way to plot a section of a plane in 3D, that is >> given by the xyz coordinates of the outline? >> >> Suppose I have a polygon - which I know for sure is a set of >> coordinates on the same plane. One method I found is to use surf.tri >> from the geometry package, and then plot the triangles with >> rgl.triangles. This method is not perfect though, because it makes the >> convex hull - no good for the polygon below. >> >> thanks for your help, >> >> Remko >> >> # Example polygon in 3D (matrix with tree columns x,y,z) >> m <- structure(c(-24.71, -36.45, -59.54, -83.97, -112.63, -126.66, >> -152.79, -171.04, -178.92, -183.71, -189.27, -191.56, -195.98, >> -203.09, -207.89, -212.12, -216.92, -221.73, -210.58, -199.43, >> -195.58, -175.38, -161.72, -152.09, -140.75, -123.63, -97.87, >> -79.04, -69.63, -61.75, -54.08, -38.34, -30.47, -24.71, -15.44, >> -13.33, -14.26, -17.39, -24.5, -31.92, -52.3, -70.45, -79.41, >> -89.16, -102.08, -111.61, -119.76, -125.55, -128.56, -132.55, >> -135.55, -138.55, -132.93, -127.31, -124.91, -125.78, -126.69, >> -127.42, -124.38, -117.74, -105.69, -88.52, -79.94, -70.97, -59.43, >> -34.75, -25.78, -15.44, 689.49, 686.54, 680.81, 674.79, 667.78, >> 664.42, 658.27, 654.05, 652.25, 651.22, 650.06, 649.66, 648.7, >> 647.04, 645.89, 644.91, 643.77, 642.63, 645.3, 647.98, 648.89, >> 653.93, 657.35, 659.75, 662.52, 666.66, 672.86, 677.25, 679.44, >> 681.24, 682.95, 686.44, 688.24, 689.49), .Dim = c(34L, 3L)) >> >> # One (wrong) way >> library(geometry) >> tm <- t(surf.tri(m, delaunayn(m))) >> plot3d(m[,1],m[,2],m[,3], type='l', col="black", size=2) >> rgl.triangles(m[tm, 1], m[tm, 2], m[tm, 3], col="green") >> >> > > There's a function triangulate() in the gpclib package that can triangulate > a 2d polygon. So you could pick two out of your three dimensions, > triangulate those, then compute the 3rd coordinate from a fitted plane to > the other two. For example: > > library(gpclib) > x <- m[,1] > y <- m[,2] > z <- m[,3] > triangles <- triangulate(as(cbind(x,y), "gpc.poly")) > zfit <- predict(lm(z ~ x + y), newdata=data.frame(x=triangles[,1], > y=triangles[,2])) > triangles3d(cbind(triangles, zfit), col="green") > > Duncan Murdoch > ______________________________________________ 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.
