Re: [NMusers] ISAMPLE under SAEM and IMP

From: Xinting Wang <wxinting1986_at_gmail.com>
Date: Mon, 13 Apr 2015 12:57:20 +0800

Dear all,

Thanks very much for your explanation.

I tried to manipulate different ISAMPLE options after your suggestion, and
found that raising ISAMPLE from 2 to 5 would not produce a convergence
[CTYPE=3], but if the number is 300, then a convergence is rapidly
achieved. Additionally, this does not have an untolerable prolongation of
computation time. While I understand that this is only a guidance, and
judgement should be made based on the outcome from .ext file produced, it
seems to me that raising the number could actually help with convergence.

A follow-up question is, does the convergence criteria in IMP meaniningful,
or similar to SAEM, a reference to .ext file is also the preferred method
to evaluate if the method is appropriate? Many thanks!

Best Regards
Xinting


On 9 April 2015 at 01:02, Bauer, Robert <Robert.Bauer_at_iconplc.com> wrote:

> Xinting Wang:
>
> Generating each sample in SAEM is computationally more expensive in SAEM,
> and so ISAMPLE of 2-10 is generally done. You may try increasing ISAMPLE=3
> or 5 in SAEM. Furthermore, convergence testing is only a guide, Review
> the .ext file and be satisfied by visual inspection that the parameters are
> not directionally changing, and are just randomly fluctuating.
>
>
>
> Robert J. Bauer, Ph.D.
>
> Vice President, Pharmacometrics R&D
>
> ICON Early Phase
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> *From:* owner-nmusers_at_globomaxnm.com [mailto:owner-nmusers_at_globomaxnm.com]
> *On Behalf Of *Xinting Wang
> *Sent:* Tuesday, April 07, 2015 7:42 PM
> *To:* nmusers_at_globomaxnm.com
> *Subject:* [NMusers] ISAMPLE under SAEM and IMP
>
>
>
> Dear all,
>
> I have a question regarding the setting of ISAMPLE under SAEM and IMP
> method in Nonmem 7.2.
>
> I have noticed that in the NONMEM manual, the default setting of ISAMPLE
> for IMP is 300, and 2 for SAEM. Well it was well explained about the
> general guidance of ISAMPLE for IMP, i.e. might need to float to 1000-3000
> in case of sparse samples. However, the setting for ISAMPLE under SAEM is
> not explained that much.
>
> Additionally, in the examples provided in the manual most of ISAMPLE
> setting is in its hundreds or more for IMP, this option under SAEM is
> mostly 2. I understand that with a lower value the computation is fast, but
> why is there's such a big difference in terms of setting sample number per
> subject?
>
> The reason I am asking this is because of a diffitulty to achieve
> convergence in the burn-in step using below estimation method:
>
>
>
>
> *$EST MET=SAEM INTER NBURN=2000 NITER=1000 PRINT=10 NOABORT NOPRIOR=0
> ISAMPLE=2 SIGL=6 CTYPE=0 SEED=150159 FILE=Saem.ext $EST MET=IMP INTER
> NITER=2000 ISAMPLE=1000 PRINT=10 SEED=150987 SIGL=6, CTYPE=3 FILE=Imp.ext *
>
> Thanks very much for your explanation.
>
> Best Regards
>
>
> --
>
> Xinting
>
>
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--
Xinting

Received on Mon Apr 13 2015 - 00:57:20 EDT

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