Plotting an ellipse in 3D
Mike White wrote:
I have been using the ellipse function from the car package and the covariance matrix to draw an ellipse around a group of points to show the confidence limits. However, the points are actually represented by 3 variables so rather than plot each pairwise combination of variables in 2D I would like to plot the 'ellipse' in 3D using the djmrgl package. Can anyone offer advice on how I can plot the surface of a 3D 'ellipse' using the covariance matrix to define the shape, so that the points inside can also be seen.
You should use rgl, rather than djmrgl. It now has most of the same functions plus a lot more. Then you can plot the ellipse as a wireframe or transparent object. See the demo(regression) example for that kind of drawing; demo(shapes3d) for ellipses. (The demo names are from memory, I don't have access to it right now.) Duncan Murdoch