RE: Obj. function is infinite (error=136)

From: "Kowalski, Ken" Subject: RE: [NMusers] Obj. function is infinite (error=136) Date: Mon, 2 Jun 2003 08:34:37 -0400 Justin, You need to correct the parameterization as Vladimir indicates (Item 2 below) but I wouldn't start there unless you have determined that the correlation between tlag and ka is the root cause of your problem. I suspect its not. Fitting etas on tlag using FOCE is notoriously difficult. As has been previously suggested, you can get rounding errors and COV step failures when incorporating tlag if an individual's tlag is closed to an observed time point. The derivative will be undefined at such change points (ie., the model is not smoothly differentiable at tlag). Thus, you may not have a stability problem at all. Since you claim FO works for you, you might try the hybrid method specifying that the eta for tlag is approximated by FO while the others use FOCE. See NONMEM Guide VII, pp 14-15. Good luck. Ken