From: Douglas J. Trainor <trainor_at_transborder.org>

Date: Thu 16 Jun 2005 - 09:45:34 EST

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 Thu Jun 16 09:56:53 2005

Date: Thu 16 Jun 2005 - 09:45:34 EST

I think Lic. Paula Gonzalez is after one ellipse representing Hotelling's T^2 with the major axis of the ellipse oriented along PC1 and minor axis oriented along PC2.

douglas

On Jun 15, 2005, at 5:27 PM, Jari Oksanen wrote:

*>
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> On 15 Jun 2005, at 23:05, pgonzalez@fcnym.unlp.edu.ar wrote:

*>
**>> Hi!, I made a plot with two variables representing the first two axis
**>> of a
**>> principle component analysis. My question is:
**>> How can I superimpose on such plot an ellipse that represent the 95%
**>> interval of
**>> confidence of scores?
**>>
**> You can't, because you don't know the confidence (or s.e.) of the
**> scores. Or this is the answer if you mean that each point in the plot
**> should be enclosed in its private confidence ellipse (some people may
**> come with ideas to get those s.e.'s: go tell the people if you find one
**> that works). On the other hand, if you want to enclose all points
**> within one ellipse, you can directly use ellipse package which requires
**> covariance matrix as input. If you prefer ellipsoid hulls, you can use
**> functions in cluster package. Package vegan has some examples of the
**> use of ellipse package (see ordiellipse there).
**>
**> Some people are hypersensitive to "principle" components (beware).
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jun 16 09:56:53 2005

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