Re: Zeros in OMEGA matrix
Gavin,
NM can not estimate the type of matrix that you have described.
I would suggest adding C(w,y). It may be poorly estimated but you can always comment that it was added to allow estimation of the others.
Hope it works out for you,
Luann
Quoted reply history
On 7/3/2015 9:58 AM, Gavin Jarvis wrote:
> Dear NMUsers
>
> I have a problem and hope someone might be able to help. In summary, is it possible for NONMEM to model an OMEGA matrix with four elements (W,X,Y,Z) such that two of the covariances are fixed to zero and the rest freely determined? I realise NONMEM can model BAND matrices, but I can't see how to fix just two covariances to zero. The final matrix structure I'm looking for would look something like...
>
> Sw
>
> C(w,x) Sx
>
> 0 C(x,y) Sy
>
> 0 C(x,z) C(y,z) Sz
>
> I hope that makes sense. If so, is it possible?
>
> Many thanks
>
> Gavin
>
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