[R] princomp and prcomp confusion
Patrick Connolly
p_connolly at ihug.co.nz
Mon Jun 26 23:47:39 CEST 2006
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
--
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
___ Patrick Connolly
{~._.~} Great minds discuss ideas
_( Y )_ Middle minds discuss events
(:_~*~_:) Small minds discuss people
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