# [NMusers] Estimation method for ETAs with POSTHOC

From: Guo, Tingjie <t.guo_at_vumc.nl>
Date: Fri, 5 May 2017 12:10:12 +0000

Dear NMusers,

I have two questions about the mathematical details on POSTHOC estimation in NONMEM. How does NONMEM actually do when doing POSTHOC (\$EST METHOD=0 MAXEVEL=0) to get ETAs? I assume but not for sure there is an objective function to be minimized, somewhat like:

Objective function = SUM(Yobs-Ypred)^2/sigma^2 + SUM(Para_i-Para_pop)^2/omega^2

Is there an objective function used in NONMEM when doing POSTHOC? If so, what is that function?

Secondly, if the answer to above is yes, letâ€™s assume the real objective function is the same as what I mentioned above. I wonder how (NONMEM does) to minimize this function? I am currently trying to do similar things in R/Python language. I tried Metropolis-Hasting algorithm and Simulated Annealing algorithm, but with some technical problems. And the result was not comparable with NONMEM as well. Can someone give me a direction for this? The more mathematically detailed the better.

Thanks!

Warm regards,
Tingjie

Received on Fri May 05 2017 - 08:10:12 EDT

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