center or scale before analyzing using pls.pcr

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