From: Ben Bolker <bolker_at_zoo.ufl.edu>

Date: Fri 03 Feb 2006 - 09:55:47 EST

axis3d()

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri Feb 03 10:05:45 2006

Date: Fri 03 Feb 2006 - 09:55:47 EST

Michael wrote:

> shape3d only gives rigid sphere... not the free form ellipsoid that I

*> want...
**>
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one or the other of us is missing something.

after running demo(shapes3d)

[to define ellipsoid3d] and rgl.clear(),

s1 <- ellipsoid3d(qmesh = TRUE, trans = diag(4)) shade3d(rotate3d(scale3d(s1, 1, 1, 2),

angle=pi/4, x=0, y=1, z=0), col = "red")

axis3d()

produces an ellipsoid with radii (1,1,2) rotated by pi/4 around the y axis. I'm too lazy to figure out how to translate a variance-covariance matrix into a scaling/rotation matrix (the scale will want to be something like eigen(v)$values*qnorm(0.975) for a 95% contour, the rotation matrix is some function of the eigenvectors), but it seems to me that this will produce any ("free form"?) ellipsoid you want.

cheers

Ben Bolker

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri Feb 03 10:05:45 2006

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