Hi Zheng, My first guess is that you have a time-varying covariate in your data set, and the way that NONMEM handles time varying covariates in the data set is that they are kept fixed until an instantaneous change when the new record appears. If your EVID=2 records change the interpretation of the covariate (either carrying an observation backward or interpolating it), then an objective function change is expected.
If you can post your control stream and a part of your data set, it would be easier to help. Thanks, Bill On Feb 15, 2016, at 5:46, "Zheng Liu" <[email protected]<mailto:[email protected]>> wrote: Dear NMusers, I intended to print out more predicted levels at the time points without observations. Therefore I inserted those lines with EVID=2 in the data set. Surprisingly after doing so, the objective function value and the fitted parameter values changed more or less. This should not be rational. Could anyone explain the reason and how to avoid it? Thanks a lot in advance! Best regards​ ​ Zheng Liu, Ph.D. Pharmacometrician (postdoc), Melbourne Royal Children's Hospital email: [email protected]<mailto:[email protected]>
