Re: [R] slightly off-topic re prcomp()

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Thu 09 Feb 2006 - 06:38:31 EST

On 2/8/2006 12:50 PM, Laura Quinn wrote:
> Hi,
>
> I was wondering if anyone could tell me why prcomp() will "Invent" modes
> of variation in a PCA on identical replicates of data? I would have
> expected 50 (or whatever number) of identical replicates to return a null
> score in such an analysis (or at the least, all variables would share the
> same PC score). This is not the case and I was wondering could someone
> point me in the direction of some literature to explain the reason behind
> this?

I think you'll need to show us an example. I just tried what I think you described, and got all the components with 0 standard deviation, as I would have expected.

Duncan Murdoch

>
> Laura Quinn
> Institute of Atmospheric Science
> School of Earth and Environment
> University of Leeds
> Leeds
> LS2 9JT
>
> tel: +44 113 343 1596
> fax: +44 113 343 6716
> mail: laura@env.leeds.ac.uk
>
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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 Feb 09 07:52:33 2006

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