R help - Feb 2004 - center or scale before analyzing using pls.pcr

Dear all,

I found pls.pcr package will give different results if the data are
centered and scaled using scale().

I am not sure about when I should scale my data, and whether the
dependent variable should be scaled. If the dependent variable is
scaled, how I give a prediction to the real data?

I appreciate for any suggestions and comments.

Best regards,

Jinsong


====(Mr.) Jinsong Zhao
Ph.D. Candidate
School of the Environment
Nanjing University
22 Hankou Road, Nanjing 210093
P.R. China
E-mail: jinsong_zh at yahoo.com

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