Thanks Joachim, that is what I thought. I wanted to be sure that I
invest time building the right model and not just some model which
works (converges) but is biased.
Neil
On Fri, Dec 4, 2009 at 3:31 AM, Grevel, Joachim
<[email protected]
<mailto:[email protected]>> wrote:
Hi Neil,
You ask:
“So my question is whether the fits, RES, WRES plots and the ofv
values have meaning even when the minimization terminates”
The answer: you bet they matter! Residual plots are the most
informative output NONMEM gives you. They should guide you when
you determine the basic structure of your model that is supported
by the data. Successful termination, covariance step, standard
errors, Eigen values, messages, warnings... are just icing on the
cake vis-a-vis the residual plots.
These are my two pennies worth of advice,
Joachim
*Joachim Grevel *
Senior Pharmacometrician
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*From:* [email protected]
<mailto:[email protected]>
[mailto:[email protected]
<mailto:[email protected]>] *On Behalf Of *Indranil
Bhattacharya
*Sent:* 03 December 2009 15:41
*To:* [email protected] <mailto:[email protected]>
*Subject:* [NMusers] Model building
Hi, I am in the process of developing a PK/PD model and have a
naive question regarding model building.
I currently do not have all the PD data and more data would be
available in the future. For the current data set, I have tried
models say A to D.
Now model A (cell kill) and B (cell kill +transduction) converges
using FOCE (no CV% but I am willing to live with that) but from
the RES and WRES plots we can clearly see that there is some bias.
The fit is OK but not great. The ofv values are around 400.
Now models B (cell cycle specific kill), C (cell + precursor cell
kill +transduction) and D (cell cycle specific + indirect response
model) do not converge using FO or FOCE methods but when I look at
the fits from the terminated runs, the fits are much better than
those obtained with Model A, and there seems very little bias.
Also the ofv values are between 160-250.
So my question is whether the fits, RES, WRES plots and the ofv
values have meaning even when the minimization terminates.
Regards
Neil
--
Indranil Bhattacharya
--
Indranil Bhattacharya
