NONMEM Users Network Archive

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Re: [FORGED] RE: question about random seed for simulation

From: Nick Holford <n.holford>
Date: Fri, 10 Mar 2017 12:30:05 +1300


A simple solution using NONMEM is to put the different designs one after
the other and separate them with an EVID=4 data item on the first dosing
record for each design. You can a DESIGN data item value for each design
which then makes it simple to use the simulated data in a subsequent
NONMEM estimation run using ACCEPT or IGNORE on the $DATA record.

That way you can do the simulation just once and be sure to have all the
random effects (ETA) identical for each subject.

Best wishes,


On 10-Mar-17 12:11, Faelens, Ruben (Belgium) wrote:
> Hi Penny,
> Nonmem indeed calculates each subject one after the other. The random
> values will therefore change. Maybe you can set the random seed every
> time you simulate t=0, based on the subject ID?
> This may also depend on your data file; have you tried ordering on
> time (so the first 50 rows are all t=0 for subject 1 to 50) ?
> This largely depends on the simulation software and its design:
> As an example: Simulo samples all subjects together at simulation
> start, after which it runs the trial design; so the same subjects are
> sampled independent of subsequent trial design.
> I do not know about other tools (TS.2, simulx, mrgsolve), maybe the
> authors of these tools can specify?
> Kind regards,
> Ruben Faelens
> *From:*owner-nmusers
> [mailto:owner-nmusers
> *Sent:* donderdag 9 maart 2017 19:19
> *To:* nmusers
> *Subject:* [NMusers] question about random seed for simulation
> Dear All
> I have finished a multiple dose simulation for 600 subjects and want
> to perform a single dose simulation (different sampling time) on the
> same subjects (same ETA as the first simulation). I used the same
> seed for the simulation step, it turned out the first subject was the
> same and the rest of the subjects are not and I am not sure whether
> this was due to the fact that the two simulation has different number
> TIME records. If so, I wonder what is the proper way to set the
> simulation seed so that the ETAs for the second simulation will be
> identical to the first one.
> I know that I could output the individual parameter estimate from the
> first simulation and import them into the second one. But I was
> thinking if the random seed can be synchronized between the two
> simulation, it could be an easier solution.
> Your help is very much appreciated!
> Thank you very much and best regards!
> **
> *Penny (Peijuan) Zhu, Ph.D.*
> Associate Director Clinical Pharmacology
> Cell: 862-926-9079
> PD Bio-Pharma CDMA
> Sandoz
> 1N025, 100 College Road West
> Princeton, NJ 08540
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Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology, Bldg 503 Room 302A
University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand
office:+64(9)923-6730 mobile:NZ+64(21)46 23 53 FR+33(6)62 32 46 72
email: n.holford
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Received on Thu Mar 09 2017 - 18:30:05 EST

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