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
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))
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