On Fri, Mar 4, 2011 at 1:47 PM, Marius Hofert <m_hof...@web.de> wrote: > Dear expeRts, > > I would like to add two points to a wireframe plot. The points have (x,y,z) > coordinates > where z is determined to be on the wireframe [same z-value]. Now something > strange > happens. One point is perfectly plotted, the other isn't shown at all. It only > appears if I move it upwards in z-direction by adding a positive number. So > somehow > it disappears in the wireframe-surface *although* the plot symbol [the cross] > has > a positive length in each dimension [I also chose cex=5 to make it large > enough so > that it should (theoretically) be visible]. > > My wireframe plot is a complicated function which I cannot post here. Below > is a minimal > example, however, it didn't show the same problem [the surface is too nice I > guess]. > I therefore *artifically* create the problem in the example below so that you > know > what I mean. For one of the points, I subtract an epsilon [=0.25] in > z-direction and > suddenly the point completely disappears. The strange thing is that the point > is > not even "under" the surface [use the screen-argument to rotate the wireframe > plot to check this], > it's simply gone, eaten up by the surface. > > How can I make the two points visible? > I also tried to use the alpha-argument to make the wireframe transparent, but > I couldn't > solve the problem. > > Cheers, > > Marius > > PS: One also faces this problem for example if one wants to make points > visible that are on "opposite sides" of the wireframe. > > library(lattice) > > f <- function(x) 1/((1-x[1])*(1-x[2])+1) > > u <- seq(0, 1, length.out=20) > grid <- expand.grid(x=u, y=u) > x <- grid[,1] > y <- grid[,2] > z <- apply(grid, 1, f) > > pt.x <- c(0.2, 0.5) > pt.y <- c(0.6, 0.8) > eps <- 0.25 > pts <- rbind(c(pt.x, f(pt.x)-eps), c(pt.y, f(pt.y))) # points to add to the > wireframe
The reason in this case is fairly obvious: you have > pts [,1] [,2] [,3] [1,] 0.2 0.5 0.4642857 [2,] 0.6 0.8 0.9259259 So the z-value for Point 1 is 0.4642857, which is less than 0.5, the minimum of the z-axis.panel.3dscatter() "clips" any points outside the range of the bounding box, so this point is not plotted. I can't say what the problem was in your original example without looking at it, but I would guess it's caused by something similar. Hope this is not too late to be useful. -Deepayan > > wireframe(z~x*y, pts=pts, aspect=1, scales=list(col=1, arrows=FALSE), > panel.3d.wireframe = function(x,y,z,xlim,ylim,zlim,xlim.scaled, > ylim.scaled,zlim.scaled,pts,...){ > panel.3dwire(x=x, y=y, z=z, xlim=xlim, ylim=ylim, zlim=zlim, > xlim.scaled=xlim.scaled, ylim.scaled=ylim.scaled, > zlim.scaled=zlim.scaled, ...) > panel.3dscatter(x=pts[,1], y=pts[,2], z=pts[,3], > xlim=xlim, ylim=ylim, zlim=zlim, > xlim.scaled=xlim.scaled, ylim.scaled=ylim.scaled, > zlim.scaled=zlim.scaled, type="p", col=c(2,3), > cex=1.8, .scale=TRUE, ...) > }, key=list(x=0.5, y=0.95, points=list(col=c(2,3)), > text=list(c("Point 1", "Point 2")), > cex=1, align=TRUE, transparent=TRUE)) > > ______________________________________________ > 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. > ______________________________________________ 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.