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I've been trying out the reversible jump functions in WinBUGS for  
variable selection and for the most part I was pleasantly surprised at  
how easy to use the interface is. Thanks Dave Lunn for a great add-on  
package!

I have run into a couple of problems/limitations I'm wondering if  
anyone knows how to solve/work around.

1) Is there a nice way to leave out the constant (intercept) term? As  
I understand it, by saying eg.

mu[1:Ncases] <- jump.lin.pred(X[1:Ncases,1:Q], k, tau.beta)

I automatically include an intercept in all models considered. It this  
true? Anyway to exclude it?

2) I would like to restrict the beta's (the hidden regression  
coeffients) to be non-negative. As things stand these beta's get a  
multinormal prior with mean 0 (correct?). Any suggestions?

Thanks!
-- 
Michael O'Dell
Phonetics
University of Tampere

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