RE: PD lag time in $DES

From: mark.e.sale@gsk.com Subject: RE: [NMusers] PD lag time in $DES Date: Thu, November 18, 2004 10:46 am Jim, This isn't easy. In simulation packages, a "pipe" is created by a long series of concatenated compartments (in ACSL is was 50), as in: DADT(1) = -K*A(1) DADT(2) = K*A(1)-K*A(2) DADT(3) = K*A(2)-K*A(3) . . . DADT(50) = K*A(49)-K*A(50) 50 compartments will give a very nice "square wave" delay effect, but is numerically very difficult for estimation, even though there is only one parameter, which describes the delay. I've used a smaller number of compartments (2 or 3), but that doesn't really give a lag/delay, more of smudging sort of effect. In $PRED, you can just do LAG = THETA() the use T-LAG But, there is not, as far as I know, an (easy) way to store what the value was at (T-LAG) using $DES. Mark Sale M.D. Global Director, Research Modeling and Simulation GlaxoSmithKline 919-483-1808 Mobile 919-522-6668