RE: Block versus diagonal omega
Hi Al,
You are probably looking for a band matrix, see the nonmem help entry on
$OMEGA:
"
An initial estimate of a diagonal block of the OMEGA matrix may have a
band symmetric form, in which case the final estimate has the same
form. E.g., with these structures for $OMEGA BLOCK(3), the 0's are
preserved:
x
0x
00x
x
xx
0xx
"
You can find a discussion on banded $OMEGA blocks with examples here:
http://www.cognigencorp.com/nonmem/nm/99jan012004.html ; keep this
http://www.mail-archive.com/[email protected]/msg00614.html in
mind.
Jeroen
Modeling & Simulation Expert
Pharmacokinetics, Pharmacodynamics & Pharmacometrics (P3) - DMPK
MSD
PO Box 20 - AP1112
5340 BH Oss
The Netherlands
[email protected]
T: +31 (0)412 66 9320
F: +31 (0)412 66 2506
www.msd.com
Quoted reply history
________________________________
From: [email protected] [mailto:[email protected]]
On Behalf Of Berg, Alexander K., Pharm.D., Ph.D.
Sent: Thursday, 02 September, 2010 22:40
To: [email protected]
Subject: RE: [NMusers] Block versus diagonal omega
Everyone -
Thank you all for your assistance in answering my question regarding the
block versus diagonal omega structure. The answers that you all
provided have been a great help thus far and are much appreciated. As a
follow-up, I was curious if someone could point me towards a reference
that would help me to figure out how to restructure the covariance into
different omega blocks. Specifically, I would like to understand the
basis and proper method for restructuring the omega block so that I may
remove selected covariance terms when simplifying from a completely
unstructured block to a more parsimonious one. Thanks again for your
help and time -
Al Berg
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