[R] trouble with prcomp()
Scott Robbins Loarie
loarie at stanford.edu
Mon Jun 14 09:35:24 CEST 2004
Thanks very much for showing me these functions,
In prcomp(), the documentation says that Value: x is "the data
multiplied by the 'rotation' matix". Using sample data:
Why does iris%*%pcprim$rotation (the data multiplied by the rotation
matrix) not equal pcprim$x?
Thanks very much,
On Mon, 14 Jun 2004, Prof Brian Ripley wrote:
> Why are you using the OPRHANED multiv library for a facility covered by
> princomp() and prcomp() in base R? The list might be able to help you
> with the latter, but no one is supporting multiv (hence its status).
> On Sun, 13 Jun 2004, Scott Robbins Loarie wrote:
> > I am having trouble using the pca function in the multiv library.
> > I am trying to generate the values found in $rproj by using $evecs to
> > calculate linear combinations of my input data. However, I have been not
> > been able to correctly calculate the $rproj values.
> > Using the following standard sample data, why does iris%*%pcprim$evecs[,]
> > not equal pcprim$rproj?
> > data(iris)
> > iris<-as.matrix(iris[,1:4])
> > pcprim<-pca(iris)
> 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)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595
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