R help - Feb 2011 - Question about the covariate Z in rhierMnlRwMixture (bayesm)

Hello!

I am using rhierMnlRwMixture from bayesm package. I would like to use
it with a categorical covariate (Z).
I have 2 clariciation questions:

1. If the covariate is categorical, do I have to represent it as dummy
variable(s)? (e.g., 2 dummy variables for a 3-level categorical
variable)?
2. Do those dummy variables have to be centered? Help file for
rhierMnlRwMixture says: "Z should not include an intercept and is
centered for ease of interpretation." But I'd thought I'd check
just
in case: does it mean that it's OK if variables in Z are not centered?


Thank you very much!
-- 
Dimitri Liakhovitski
Ninah Consulting
www.ninah.com