Re: Simulations with OMEGA BLOCK

On 10/8/2013 4:22 AM, Lindauer, A (Andreas) wrote: > Hi NMUSERS, > I have a question regarding the use of OMEGA BLOCK statements in > simulations when one (or more) elements of the matrix are 0. > When I use the following lines to describe the OMEGA structure and run > the simulation everything works well: > $OMEGA > 0 FIX ; IIV_CL2 > 0.1 ; IIV_V2 > 0.1 ; IIV_F1 > 0.01 ; IIV_KA > $OMEGA BLOCK(1) 0.01 ; IOV_KA > $OMEGA BLOCK(1) SAME > $OMEGA BLOCK(1) SAME > $OMEGA BLOCK(1) SAME > However, rewriting the above as a full matrix gives me an error message: > $OMEGA BLOCK(8) > 0 FIX > 0 0.1 > 0 0 0.1 > 0 0 0 0.01 > 0 0 0 0 0.01 > 0 0 0 0 0 0.01 > 0 0 0 0 0 0 0.01 > 0 0 0 0 0 0 0 0.01 > NM-TRAN MESSAGES > AN ERROR WAS FOUND IN THE CONTROL STATEMENTS. > AN ERROR WAS FOUND ON LINE 75 AT THE APPROXIMATE POSITION NOTED: > 0 0 0 0 0 0 0 0.01 > 224 A VARIANCE IS ZERO, BUT THE BLOCK IS NOT FIXED TO ZERO. > I tried numerous different ways of placing the term FIX in the block, or > not mentioning it at all – nothing worked, except replacing the 0 > diagonal element by a very small number. I know that there are certain > constrains of using 0 values in an OMEGA BLOCK (band symmetric form), > but I always thought this was only relevant for estimation. > Has anyone come across a similar issue when simulating? > Best regards, Andreas. > *Andreas Lindauer, Ph.D.* > Associate Principal Scientist, Clinical PKPD > Pharmacokinetics, Pharmacodynamics, and Drug Metabolism > *Merck & Co. / MSD * > > 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 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.