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$uniq), 3)
Unfortunately I still haven't received the book I ordered, so I can't
look
this up.
Two questions:
1) What does the update() do? I mean, what happens if I replace it with
factanal(covmat = ability.cov, factors = 2)
2) What does the last command, the formulae in round() mean? I tried it
and it produced a matrix that looks kind of like correlation matrix of
some sort...
Cheers,
Kevin
------------------------------------------------------------------------------
Ko-Kang Kevin Wang
Postgraduate PGDipSci Student
Department of Statistics
University of Auckland
New Zealand
Homepage: http://www.stat.auckland.ac.nz/~kwan022
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at
stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
On Thu, 29 Aug 2002, Ko-Kang Kevin Wang wrote:> Hi, > > I had a look at the MASS4 scripts in the MASS package, in Ch 11.3 Factor > Analysis, there is a section of codes like: > > data(ability.cov) > > ability.FA <- factanal(covmat = ability.cov, factors = 1) > ability.FA > (ability.FA <- update(ability.FA, factors = 2)) > #summary(ability.FA) > round(loadings(ability.FA) %*% t(loadings(ability.FA)) + > diag(ability.FA$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 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
Dear Kevin, At 09:55 PM 8/29/2002 +1200, Ko-Kang Kevin Wang wrote:>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$uniq), 3) > >Unfortunately I still haven't received the book I ordered, so I can't look >this up.I, too (and I'm sure many others) are also waiting.>Two questions: > >1) What does the update() do? I mean, what happens if I replace it with > factanal(covmat = ability.cov, factors = 2)As is generally the case, update methods allow you to respecify a model, here a factor analysis, changing some arguments to the modeling function. As you probably discovered, factanal(covmat = ability.cov, factors = 2) is equivalent.>2) What does the last command, the formulae in round() mean? I tried it >and it produced a matrix that looks kind of like correlation matrix of >some sort...These are the reproduced correlations, which may be compared with the observed correlations, round(ability.FA$correlation, 3). I hope that this helps, John ----------------------------------------------------- John Fox Department of Sociology McMaster University Hamilton, Ontario, Canada L8S 4M4 email: jfox at mcmaster.ca phone: 905-525-9140x23604 web: www.socsci.mcmaster.ca/jfox ----------------------------------------------------- -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._