[R] how to create contour lines on a 3D surface plot by persp3d from rgl package

[Duncan Murdoch]

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On 20/08/2015 5:20 PM, Aki Hoji wrote:
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> 
> HI,
> 
> I created a 3D surface plot of 2D surface data (generated by kde2d)
> by using persp3d from rlg as follows;
> 
> 
> persp3d(dens3d, theta=50, phi=25, expand=0.75, col=color[zcol],
> ticktype="detailed",axes=TRUE)
> 
> I would like to add contour lines to this 3D surface plot and I’d
> appreciate if any help on this.
> 
> Thanks in advance.

Use the contourLines() function to compute them, then plot them using
lines3d.

The difficulty is that they may be hidden by the surface.  The
simplest way around that is to make the surface have partial
transparency.  If you don't want to do that, plotting the lines first
will

For example:

f <- function(x, y) x^2 + y^2
x <- seq(-2, 2, len=50)
y <- seq(-2, 2, len=50)
z <- outer(x,y,f)
persp3d(x,y,z, col="red",alpha=0.5)
lines <- contourLines(x, y, z)
for (i in seq_along(lines)) {
  x <- lines[[i]]$x
  y <- lines[[i]]$y
  z <- rep(lines[[i]]$level, length(x))
  lines3d(x, y, z)
}


Duncan Murdoch
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