[R] Factor Analysis in MASS4

[Ko-Kang Kevin Wang]

I see.

Just out of interest, is it possible to do a regresion analysis on the
factors obtained from the factor analysis?

On Thu, 29 Aug 2002 ripley at stats.ox.ac.uk wrote:

> Date: Thu, 29 Aug 2002 11:38:08 +0100 (BST)
> From: ripley at stats.ox.ac.uk
> To: Ko-Kang Kevin Wang <kwan022 at stat.auckland.ac.nz>
> Cc: R Help <r-help at stat.math.ethz.ch>
> Subject: Re: [R] Factor Analysis in MASS4
> 
> On Thu, 29 Aug 2002, Ko-Kang Kevin Wang wrote:
> 
> > Hi,
> >
> > I had a look at the MASS4 scripts in the MASS package, in Ch 11.3 Factor
> > Analysis, there is a section of codes like:
> >
> >   data(ability.cov)
> >
> >   ability.FA <- factanal(covmat = ability.cov, factors = 1)
> >   ability.FA
> >   (ability.FA <- update(ability.FA, factors = 2))
> >   #summary(ability.FA)
> >   round(loadings(ability.FA) %*% t(loadings(ability.FA)) +
> >              diag(ability.FA$uniq), 3)
> >
> > Unfortunately I still haven't received the book I ordered, so I can't look
> > this up.
> >
> > Two questions:
> >
> > 1) What does the update() do?  I mean, what happens if I replace it with
> >      factanal(covmat = ability.cov, factors = 2)
> 
> That's what it does.  update always recalls the original call with the
> changes as given.
> 
> > 2) What does the last command, the formulae in round() mean?  I tried it
> > and it produced a matrix that looks kind of like correlation matrix of
> > some sort...
> 
> It is the fitted correlations.
> 
> 
> -- 
> 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 272860 (secr)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> 
> 

Cheers,

Kevin

------------------------------------------------------------------------------
Ko-Kang Kevin Wang
Postgraduate PGDipSci Student
Department of Statistics
University of Auckland
New Zealand
Homepage: http://www.stat.auckland.ac.nz/~kwan022


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