www-ai.cs.tu-dortmund.de/de/LEHRE/VORLESUNGEN/NOPT/SS14/code/contour_quad.html
nrow=2, ncol=2) # convex, axis-aligned M[[3]] <- matrix(c(10,0,0,1), byrow=TRUE, nrow=2, ncol=2) # convex, axis-aligned, ill-conditioned M[[4]] <- matrix(c(10,3,3,5), byrow=TRUE, nrow=2, ncol=2) # convex [...] urces/tscu3dg.R # showsurface <- function(x, y, z) { persp3d(x,y,z, col="red", alpha=0.4, axes=TRUE) contours <- contourLines(x,y,z) for (i in 1:length(contours)) with(contours[[i]], lines3d(x, y, level [...] level, col="darkred")) } open3d() showsurface(x,y,z) d <- eigen(M) w <- 2* abs(d$values) / sum(abs(d$values)) lines3d(w[1]*c(min(x),max(x))*d$vectors[1,1], w[1]*c(min(y),max(y))*d$vectors[2,1], c(0,0), c …