Re: Box-Cox transformation in NONMEM

From: stuart@c255.ucsf.EDU (S.Beal) Subject: Re: Box-Cox transformation in NONMEM Date: 29 Sep 1998 19:01:54 -0400 Subject: Transform-both-sides We do have some experience with this. Here is a set-up using the Box-Cox power transformation and homoscedastic (uncorrelated, univariate) epsilon error on the transformed scale. It can be modified for other transformations. The set-up requires two user-routines, the use of which is not supported by the NPG. These routines are included. If X gives the prediction for an observation (based on the eta values) Use the statement Y=(X**THETA(xxx)-1)/THETA(xxx)+ERR(1) to set Y in abbreviated code, where xxx is the index of that element of theta serving as the lambda parameter. Include the options OTHER=CONTR OTHER=CCONTR in the $SUBROUTINES record, and the two user routines: subroutine contr (icall,cnt,ier1,ier2) double precision cnt call ncontr (2,cnt,ier1,ier2) return end subroutine ccontr (icall,c1,c2,c3,ier1,ier2) parameter (lth=40,lvr=30) common /rocm0/ theta (lth) common /rocm4/ y double precision c1,c2,c3,theta,y,w,one,two dimension c2(*),c3(lvr,*) data one,two/1.,2./ if (icall.le.1) return w=y y=(y**theta(xxx)-one)/theta(xxx) call cels (c1,c2,c3,ier1,ier2) y=w c1=c1-two*(theta(xxx)-one)*log(y) return end in the NONMEM executable.