[R-sig-eco] PCA

[Stephen Sefick]

Is it an assemblage that you are trying to ordinate?  If so, you can use 
the hellinger transformation that is avaliable in the decostand function 
of vegan to transform the data so that when you ordinate it you will 
then have euclidean distances.  See Legendre and Gallagher 2001 for the 
relevant discussion.
FWIW,

Stephen

On 03/03/2012 03:45 PM, Sami Rabei wrote:
> Dear All
>
> If I have a similarity matrix, It is possible to have a PCA (Principal
> component for it.
>
>
>
> Sami Rabei
>
> http://mansoura.academia.edu/SamiRabei
>
>
>
>
> ----------------------------------
> With my Best Wishes
> Sami Hussein Rabei, Ph.D.
> Botany Department
> Faculty of Science at Damietta
> New Damietta , Post Box 34517
> Damietta
> Egypt .
>
> Tel. Mobile:  002 0127 3601618
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>
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-- 
Stephen Sefick
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Let's not spend our time and resources thinking about things that are so little or so large that all they really do for us is puff us up and make us feel like gods.  We are mammals, and have not exhausted the annoying little problems of being mammals.

                                 -K. Mullis

"A big computer, a complex algorithm and a long time does not equal science."

                               -Robert Gentleman