princomp and prcomp confusion

From: Patrick Connolly

When I look through archives at


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.

>From what I can gather by googling around about R-mode and Q-mode PCA,
the current description should be the correct one.

Andy


best

--


Patrick Connolly
{} Great minds discuss ideas
_( Y )_ Middle minds discuss events
(::) Small minds discuss people
(_)-(_) Anon





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