RE: basic questions...
Paola,
I agree with Nick that there may be little use for the DEL and W variables.
The standard coding may be something like:
$ERROR
IPRED = F
IRES = DV-IPRED
W = THETA(#)*F
DEL = 0
IF(W.EQ.0) DEL = 1
IWRES = IRES/(W+DEL)
Y = F+EPS(1)*W
The W represents the “weight” of the error model. In the above example this is
proportional error.
The DEL is used to keep the unlikely divide by zero error from appearing when
IRES/W is calculated. When W=0, IRES=RES.
Like Nick, I’m don’t find too much use in this. If W = 0, I think the IWRES
should be missing instead of calculated as RES.
Matt.
Quoted reply history
From: [email protected] [mailto:[email protected]] On
Behalf Of Nick Holford
Sent: Thursday, March 31, 2011 9:03 AM
To: nmusers
Subject: Re: [NMusers] basic questions...
Paola,
On 31/03/2011 3:02 p.m., di Gion, Paola wrote:
Dear NONMEM users,
as beginners in NONMEM we have the following questions:
- What is the meaning of "DEL" and "W" (in the subroutine $ERROR)?
They are sort of like a virus that is spread by copying and pasting from old
control streams passed around among beginners.
These are not standard NM-TRAN variables. Some people like to use them to
create some diagnostic variables like IWRES. I find no use for them.
- What is the meaning of "TOL" and when should it be used?
TOL is an option for the differential equation solving subroutines (ADVAN6,
ADVAN8, ADVAN9 and ADVAN13 (NM7 only).
It specifies the tolerance for the numerical solution of the differential
equations. A reasonable starting value is TOL=6 for NM7 (with NSIG=2 and
SIGL=6).
- Assumed we need to use $DES, is this possible only with NONMEM version 7 or
can we use it also in NONMEM 6?
You can use $DES with any version of NONMEM. It usually runs faster with NM6
than NM7. However, in some cases ADVAN13 in NONMEM7 will run faster than
ADVAN6,8.9. Its hard to predict which ADVAN is best so just try different ones
and use the one that runs fastest.
Thanks a lot and kind regards from rainy Cologne
Its raining in Cape Town too!
Paola & Lisa
--
Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology
University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand
tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53
email: [email protected]<mailto:[email protected]>
http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford
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