From: Deepayan Sarkar <deepayan.sarkar_at_gmail.com>

Date: Wed, 30 Mar 2011 14:22:34 +0530

R-help_at_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. Received on Wed 30 Mar 2011 - 09:02:49 GMT

Date: Wed, 30 Mar 2011 14:22:34 +0530

On Fri, Mar 4, 2011 at 1:47 PM, Marius Hofert <m_hofert_at_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_at_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.
**>
*

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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. Received on Wed 30 Mar 2011 - 09:02:49 GMT

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