What is pi?

[berg1546]

Hello,

A friend sent me this portion of his code and I'm trying to understand what the parameter 'pi' is in the RDHFHet model:

S.treat.spec.t.gap=list(formula=~treat*spec*t.gap)
p.c.diff.treat.spec.session=list(p=list(formula=~treat*spec*session,share=FALSE),c=list(formula=~treat*spec*session))
pi.treat.spec.session=list(formula=~treat*spec*session)

Thanks in advance,
Sergey

[jlaake]

If you ever have a question like this, your best bet is to look in Cooch and White (see chapter 14). In the mixture models, pi is the proportion in each mixture. If there are k mixtures then there are k-1 pi's with pi_k=1-sum of the k-1 pi's.

--jeff