[R-sig-eco] manipulating PCA output in R

[David Hewitt]

> I am doing a PCA on a single dataset and want to control which variables
> are plotted as vectors on the biplot produced. How can I first determine
> which variables are most important in producing the ordination and how do
> I then control what variables are included as vectors in the biplot?
> 

I'm not sure what you mean by "most important", but I think you want to know
the loadings on the components, which you can retrieve easily from the
object returned by princomp or prcomp (it depends on which function you
used). See ?prcomp and ?princomp. With prcomp the rotations are printed by
default. With princomp, use loadings(princomp.object).

Not sure about suppressing certain arrows (variables) from the plot.

-----
David Hewitt
Research Fishery Biologist
USGS Klamath Falls Field Station (USA)
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