Re: Fwd: T in $DES
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 next 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 fine.
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
Quoted reply history
> On 6 Jul 2021, at 14:44, Matts Kågedal <[email protected]> wrote:
>
> 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 the
> patient? I was expecting it to be Zero (same as Time). Seems to be the same
> 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>
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