Dennis, I would be curious if you get the same difference in OF value if you do the following for the ADVAN6 version:
Same initial estimates between the 2 ADVANs $ESTIMATION use the options SORT, SIGDIG=3, SIGL=9 $SUBROUTINE ADVAN6 TOL=9 If $ERROR is %CV or Log error model, include DFLAG=0 IF(CMT.EQ.DOSING CMT) DFLAG=1 For the %CV set IPRED=F+DFLAG For Log error set IPRED=LOG(F+DFLAG) This helps handle the first oral dose record more consistently between advan4 and advan6 Over the years, I've seen differences for the same model between 2 advans become more similar. Luann Phillips Distinguished Scientist, Pharmacometrics Cognigen Corporation, a Simulations Plus company From: owner-nmus...@globomaxnm.com <owner-nmus...@globomaxnm.com> On Behalf Of Dennis Fisher Sent: Wednesday, September 23, 2020 8:36 PM To: Mark Tepeck <mark.tep...@gmail.com> Cc: nmusers@globomaxnm.com Subject: Re: [NMusers] OFV from different algorithms Mark I posed a variant of this question to Stu Beal (Sheiner's statistician) > 20 years ago. He answered that one cannot compare ADVAN's, e.g., between ADVAN4 and ADVAN6 for the identical model. I verified this today when I ran a model with those two ADVAN's -- both converged, they yielded quite similar parameter estimates, but the OF differed by 60 units. I will be interested to hear Bob Bauer's reply to this issue. Dennis Dennis Fisher MD P < (The "P Less Than" Company) Phone / Fax: 1-866-PLessThan (1-866-753-7784) www.PLessThan.com<http://www.plessthan.com/> On Sep 23, 2020, at 5:09 PM, Mark Tepeck <mark.tep...@gmail.com<mailto:mark.tep...@gmail.com>> wrote: Hi NMusers, I believe below is a very common question, but I could not find a clear answer in literature. Sometimes, we want to find out which algorithm offers the better model fitting for a given dataset. Is it possible to use the objective function value (OFV) to compare the model fitting computed by various algorithms (e.g. FOCE, IMP, and SAEM) ? Put it into another way, the same input dataset with the same fitted model/estimates will lead to similar OFVs among FOCE, IMP, and SAEM? Thanks, Mark
