Message-ID: <Pine.LNX.4.31.0208291136450.16061-100000@gannet.stats>
Date: 2002-08-29T10:38:08Z
From: Brian Ripley
Subject: Factor Analysis in MASS4
In-Reply-To: <Pine.SOL.4.21.0208292151020.98-100000@stat1.stat.auckland.ac.nz>
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
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