Message-ID: <7oisil98b4.fsf@foo.nemo-project.org>
Date: 2004-02-05T09:36:47Z
From: Bjørn-Helge Mevik
Subject: center or scale before analyzing using pls.pcr
In-Reply-To: <20040204191828.34792.qmail@web20813.mail.yahoo.com> (Jinsong Zhao's message of "Wed, 4 Feb 2004 11:18:28 -0800 (PST)")
Jinsong Zhao <jinsong_zh at yahoo.com> writes:
> I found pls.pcr package will give different results if the data are
> centered and scaled using scale().
Centering is done automatically by all implementations of PLSR I am
aware of (including pls.pcr, afaics).
> I am not sure about when I should scale my data,
There are no fixed rules about this. Many practitioners live more or
less by the rule that unless the variables are `of the same type' or have
equal or comparable scales, they are scaled. One example of data that
is typically not scaled (at least to begin with) is spectroscopic data.
> and whether the dependent variable should be scaled.
There is no need for scaling the dependent variable.
--
Bj?rn-Helge Mevik