NONMEM Users Network Archive

Hosted by Cognigen

RE: covariance step

From: Hang, Yaming <yaming_hang>
Date: Thu, 16 Jul 2009 16:06:11 -0400

Hi Varsha,

You may need to fix some of the OMEGAs. During a recent simulation
exercise, I used the true model to fit data randomly generated from a
model and the same message showed up. I fixed the OMEGA for one
parameter which the data has limited information on and the covariance
step became successful.

Hope this helps,
Yaming

-----Original Message-----
From: owner-nmusers
On Behalf Of Varsha Mehta
Sent: Thursday, July 16, 2009 1:21 PM
To: nmusers
Subject: [NMusers] covariance step


Dear NONMEM users:

I have a data set for 30 infants where I am running a 2 COMPT PK model.
I got the following error message for the covariance step. I need some
help with trying to fix this error. Any suggestions? should I increase
the upper boundries of initial estimates?



MINIMIZATION SUCCESSFUL
 NO. OF FUNCTION EVALUATIONS USED: 289
 NO. OF SIG. DIGITS IN FINAL EST.: 3.0
0PARAMETER ESTIMATE IS NEAR ITS BOUNDARY
 THIS MUST BE ADDRESSED BEFORE THE COVARIANCE STEP CAN BE IMPLEMENTED

any help is appreciated.
Thanks


Varsha Mehta, MS(CRDSA), Pharm.D., FCCP
Clinical Associate Professor
Pharmacy, Pediatrics and Communicable Diseases
Clinical Pharmacist Neonatal Critical Care
University of Michigan
(O) 734-936-8985
(F) 734-936-6946
varsham

**********************************************************
Electronic Mail is not secure, may not be read every day, and should not
be used for urgent or sensitive issues
Notice: This e-mail message, together with any attachments, contains
information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station,
New Jersey, USA 08889), and/or its affiliates (which may be known
outside the United States as Merck Frosst, Merck Sharp & Dohme or
MSD and in Japan, as Banyu - direct contact information for affiliates is
available at http://www.merck.com/contact/contacts.html) that may be
confidential, proprietary copyrighted and/or legally privileged. It is
intended solely for the use of the individual or entity named on this
message. If you are not the intended recipient, and have received this
message in error, please notify us immediately by reply e-mail and
then delete it from your system.
Received on Thu Jul 16 2009 - 16:06:11 EDT

The NONMEM Users Network is maintained by ICON plc. Requests to subscribe to the network should be sent to: nmusers-request@iconplc.com.

Once subscribed, you may contribute to the discussion by emailing: nmusers@globomaxnm.com.