[R] Factor Analysis in MASS4

[ripley@stats.ox.ac.uk]

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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