Help.....
Got the following message from a colleague
Can anyone suggest a solution please?
regards
simonf
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Dear Simon
For years I've been explaining principle components analysis to my ecology
students using a mixture of chalk-and-talk and overheads, but it strikes me
that it will be difficult to do properly unless it's converted into
web-pages. The basic problem is this
1. Plot a 3-D scatter graph of about 15 points, with the x, y, z axes
representing species A, B and C. (In reality the technique is used in 50+
dimensions but for obvious reasons I can't plot that!). It will vastly
assist the students' understanding if I can rotate this plot slowly around
its y axis, so some sort of animation functionality might be needed to do
this.
2. Stick a line onto the scatter of points (representing the first
principle component). Again rotate the plot in real-time.
3. Draw short lines from my points at 90 degrees to my first component.
(and rotate the plot)
4. Draw a second line at 90 degrees to the first, and repeat.
5. Draw an entirely new graph, now only in 2 dimensions of the PCA plot.
We've now compressed the data from 3 to 2 dimensions with minimal loss of
information.
I'm happy to write some Java if this is essential (I have access to
JBuilder) but would prefer not to, as I've no idea how to get the
scatter-plot to rotate. I assume that one of the new 3-D animation
packages for web authoring would be better. Can you give any advice?
Many thanks
Roy
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Learning Technology Co-ordinator
University of Newcastle
Tel: 0191-222-5183
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