[R] plotting other axes for PCA

[Prof Brian Ripley]

On Fri, 18 Jan 2008, Silvia Lomascolo wrote:

>
> Hi R-community,
> I am doing a PCA and I need plots for different combinations of axes (e.g.,
> PC1 vs PC3, and PC2 vs PC3) with the arrows indicating the loadings of each
> variables.  What I need is exactly what I get using biplot (pca.object) but
> for other axes.

The prcomp and princomp methods of biplot() have argument 'choices' that 
does exactly what you seem to be asking for.

> I have plotted PC2 and 3 using the scores of the cases, but I don't get the
> arrows proportional to the loadings of each variables on each axis.
>
> Any hints on this?
>
> Thanks, Silvia.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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