[R] slightly off-topic re prcomp()

[Duncan Murdoch]

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 at env.leeds.ac.uk
> 
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