[R] center or scale before analyzing using pls.pcr

[Bjørn-Helge Mevik]

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.

-- 
Bjørn-Helge Mevik