[R] princomp and prcomp confusion

[Patrick Connolly]

When I look through archives at
https://stat.ethz.ch/pipermail/r-help/2003-October/040525.html

I see this:

Liaw, Andy wrote:

>In the `Detail' section of ?princomp:
>
>princomp only handles so-called Q-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 R-mode PCA
>use prcomp. 
>

It doesn't appear that anyone disputed the accuracy of it.


My current installation (version.string Version 2.3.1 (2006-06-01))
says in the detail of princomp


     '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'.

I've not been following principal components and have only recently
had a use for that methodology.  Am I to assume that the later version
is the correct one?  I thought I'd worked out what the distinction
between R-mode and Q-mode was, but now I'm as confused as ever.

best

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