On Mon, Oct 19, 2009 at 5:02 AM, Mark Difford <mark_diff...@yahoo.co.uk> wrote: > > Peng Yu wrote: > >>> Some webpage has described prcomp and princomp, but I am still not >>> quite sure what the major difference between them is. > > The main difference, which could be extracted from the information given in > the help files, is that prcomp uses the singular value decomposition [i.e. > does not rely eigenanalysis], which "is generally the preferred method for > numerical accuracy." > > There is plenty of information on the web about the differences between R- > and Q-mode PCA.
If prcomp is always better than princomp, why there is still princomp in R? Are there any cases in which I should use princomp instead of prcomp? I don't find the argument 'cor' in prcomp as in princomp. Is 'cor' available in prcomp? I'm reading the book Principle Component Analysis by I.T. Jolliffe. But I don't find the relevant discussion on R-mode and Q-mode. Would you please point me a good reference on this? >> Some webpage has described prcomp and princomp, but I am still not >> quite sure what the major difference between them is. Can they be used >> interchangeably? >> >> In help, it says >> >> 'princomp' only handles so-called R-mode PCA, that is feature >> extraction of variables. If a data matrix is supplied (possibly >> via a formula) it is required that there are at least as many >> units as variables. For Q-mode PCA use 'prcomp'. >> >> >> What are R-mode and Q-mode? Are they just too different numerical >> methods to compute PCA? >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> >> > > -- > View this message in context: > http://www.nabble.com/What-is-the-difference-between-prcomp-and-princomp--tp25952965p25955831.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
