Re: Question regarding Calculation Process in $DES BLOCK
Hi Lili,
In addition to the information Paul provided.
DDTI for a specific row should be the last value of T (continuous time) that the integration step took. This may not match the event time identically. As NONMEM is performing numerical integration between two event times T is taking on many values between the two event times (TIME, discrete). During this process, it may actually require taking a step that goes a small amount past the 2nd event time.
Best regards,
Luann Phillips
Director, PK/PD
Cognigen Corporation
(716) 633-3463 ext. 236
Paul Matthias Diderichsen wrote:
> Hi Lili,
>
Quoted reply history
> On 5/26/2011 1:52 AM, Li Li wrote:
> > When I output DDT1, the table will be:
> > Subject Time (hr) DDT1
> > 1 0 4???
> [...]
> > 2 0 5???
> [...]
> > Why the DDT1 for subject 1 at first time point is 4 and subject 2 at
> > first time point is 5? Why it holds the last time point value of each
> > subject?
>
> In the output, nonmem tells you that this is going to happen:
>
> "
>
> (WARNING 48) DES-DEFINED ITEMS ARE COMPUTED ONLY WHEN EVENT TIME INCREASES. E.G., DISPLAYED VALUES ASSOCIATED WITH THE FIRST EVENT RECORD OF AN INDIVIDUAL RECORD ARE COMPUTED WITH (THE LAST ADVANCE TO) AN EVENT TIME OF THE PRIOR INDIVIDUAL RECORD.
>
> "
>
> A related caveat is that during integration between two time points, the value of data items (in the $DES block) are set to the values defined at the end time, not the start time.
>
> I'm afraid that I can't give you a good explanation for this design decision.
>
> Kind regards,