Re: [R] ellipse -confidence interval

From: Jari Oksanen <jari.oksanen_at_oulu.fi>
Date: Thu 16 Jun 2005 - 07:27:38 EST

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).

cheers, jari oksanen

--
Jari Oksanen, Oulu, Finland

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Received on Thu Jun 16 07:33:04 2005

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