Re: st: Cross-classified Random Coefficient Model with xtmelogit

[Troy Hegel <troy.hegel@bio.uio.no>]

Thank you very much Bobby for your speedy response.

Your suggested work around does indeed work fine. And yes, the "5" in my 
original post was a typo and should have been a "7", my apologies for that.

Regards,

Troy

> ------------------------------
>
> Date: Tue, 15 Apr 2008 14:42:19 -0500
> From: rgutierrez@stata.com (Roberto G. Gutierrez, StataCorp)
> Subject: Re: st: Cross-classified Random Coefficient Model with xtmelogit
>
> Troy Hegel <troy.hegel@bio.uio.no> writes:
>
>   
> > I am trying to fit a cross-classified mixed model in which Herd (n=10) and
> > Year (n=27) are cross-classified random effects. The number of observations
> > for my model is 165.
> >     
> [...]
>
>   
> > Using the following syntax I can fit a cross-classified random intercept
> > model that yields sensible results:
> >     
>   
> > xtmelogit Calves Treat Adj April || _all:R.Year || Herd: , binomial(Cows)
> >     
>   
> > I am trying to fit "April" as a random coefficient on "Herd" and I thought
> > that this syntax should work, but I get the subsequent error message:
> >     
>   
> > xtmelogit Calves Treat Adj April || _all:R.Year || Herd: April ,
> > binomial(Cows)
> >     
> [...]
>
>   
> > initial vector: matrix must be dimension 5 r(503);
> >     
> [...]
>
> Troy's syntax is indeed correct for the model he wishes to fit.  Instead, he
> has uncovered a bug in the initial-values logic for -xtmelogit-, a bug that
> can be triggered in the specific case of cross-classified random effects
> models with random coefficients in addition to random intercepts.
>
> We'll fix this in the next ado update.  In the meantime, Troy can work around
> this bug by supplying his own initial values and by-passing the initial values
> calculation altogether.  A vector of zeros should suffice, if not, Troy can
> email me privately and I can suggest some alternatives.
>
>    . mat b = J(1, 7, 0)
>    . xtmelogit Calves Treat Adj April || _all:R.Year || Herd: April ,
>                binomial(Cows) from(b)
>
> The "7" in the above is for four fixed effects (three coefficients plus one
> intercept) and three variance components; one at the Year level and two at the
> Herd level (one random intercept and and one random coefficient on April).
> Troy's error message indicates this number as "5", but it should be "7", and
> in my tests to reproduce the bug it was.  In any case, the discrepancy won't
> matter once the bug is fixed.
>
> - --Bobby
> rgutierrez@stata.com
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