Re: Fwd: T in $DES

On 6 July 2021 at 10:54:45 pm, Matts Kågedal (mattskagedal wrote: Thanks Jakob and Dennis for helpful comments! I think the model is doing what it should. My problem is that I don't get an accurate output of the covariate prediction at time zero when computed inside $DES based on T_DAY (where T_DAY=T). As a workaround I now also derive the predicted covariate value in $PK based on TIME (from the dataset) just for output in $TABLE. This seems to be working. Thanks, Matts On Tue, Jul 6, 2021 at 3:15 PM Jakob Ribbing <jakob.ribbing > wrote: > Dear Matts, > > Did you get funny results in the way that using T_DAY did now work as > intended? > If you are unsure you could set up a simple test where you have the > analytical solution to the output, as an initial confirmation. > > Otherwise, for models integrating forward in time, a covariate value at > time zero (or subjects first time point) would not have an impact on the > model fit or parameter value, as nonmem would look forward towards the ne xt > record in time. > $DES isspecial since the solver may move back and forth and time is > updated in-between data records, but what you try to do may still work fi ne. > The output in the table at time zero would be the subject’s last value > because it has not yet entered $DES at time zero, but integrating forward > that should not impact the fit (I believe). > > Best regards > > Jakob > > > > > On 6 Jul 2021, at 14:44, Matts Kågedal <mattskagedal e: > > Hi all, > I have a question regaring T in $DES. > I have a time-varying covariate that is derived based on an explicit > equation and then use in a differential equation. > I got some funny results in the output table and investigated a bit > further. > > I therefore derived T_DAY=T in $DES as below and output it in $TABLE. > Why is T_DAY at TIME=0 equal to the time of the last observation for th e > patient? I was expecting it to be Zero (same as Time). Seems to be the sa me > for all IDs in the dataset. > Below is the output created in $TABLE including the "derived" variable > T_DAY. > Any advice would be appreciated. > Matts Kågedal > > <image.png> > > <image.png> > > > > *This communication is confidential and is only intended for the use of > the individual or entity to which it is directed. It may contain > information that is privileged and exempt from disclosure under applicabl e > law. If you are not the intended recipient please notify us immediately. > Please do not copy it or disclose its contents to any other person.* > *Any personal data will be processed in accordance with Pharmetheus' > privacy notice, available here https://pharmetheus.com/privacy-policy/. * >