[R] What is the difference between prcomp and princomp?

[Peng Yu]

On Mon, Oct 19, 2009 at 5:02 AM, Mark Difford <mark_difford at 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?
>>
>> ______________________________________________
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>> 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.
>>
>>
>
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> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>