RE: Log-transformation

From:"Kowalski, Ken" Subject:RE: [NMusers] Log-transformation Date:Wed, 9 Apr 2003 08:04:41 -0400 Vladimir, I'm not sure what you are trying to say regarding the log(0) problem and 2-comp simulation vs 1-comp model fitting. These are two separate issues. For the model that Beal proposed below if F is a valid PK model prediction (F>=0) and M=THETA(n) is constrained to be greater than 0 on the $THETA record then it should avoid the log(0) problem. I must confess that I don't have a lot of experience with this model as I was merely suggesting it to Luann as another option based on my reading of Beal's paper in the situation where one wants to use the log-transformed-both-sides approach but F=0 is a valid prediction such as when one incorporates a Tlag parameter where for some t, t<Tlag. It may be that in some cases NONMEM may wish to estimate THETA(n) to a lower bound of 0 in which case the log(0) problem would still exist. Ken