Log-transformation

From:Daniel Corrado Subject: [NMusers] Log-transformation Date:Mon, 31 Mar 2003 13:26:32 -0800 (PST) Hello! I am trying to fit data to a 2-compartment model after log transformation. My initial runs were without log transformation. The data fits ok but I was advised to fit it after log transformation. Transforming DV to LogDV gives negative values to concentrations below 1.0. Is this a problem? Though I got successful minimization prior to log transformation, when I try to run Nonmem (using PDx-POP) after log transformation nothing happens. I wanted to find out whether it was the negative log values or something in my control stream that is causing the problem. Thanks, Dan My control stream is as follows. ;Model Desc: base model run 1 ;Project Name: population run ;Project ID: EN-001 $PROB RUN# 801 (TWO COMP PK MODEL) $INPUT C ID TIME DV AMT $DATA 801.csv IGNORE C $SUBROUTINES ADVAN4 TRANS 1 $PK TVKA = THETA(1) TVK = THETA(2) TVK23 = THETA(3) TVK32 = THETA(4) TVV2 = THETA(5) KA=EXP(TVKA)*EXP(ETA(1)) K=EXP(TVK)*EXP(ETA(2)) K23=EXP(TVK23)*EXP(ETA(3)) K32=EXP(TVK32)*EXP(ETA(3)) V2=EXP(TVV2)*EXP(ETA(4)) S2=V2 $ERROR Y=LOG(F)+ERR(1) $THETA (0, 0.39); KA (0, 0.3); K (0, 0.048); K23 (0, 0.023); K32 (0, 1250); V2 $OMEGA 0.1 ;[P] INTERIND VAR IN KA 0.1 ;[P] INTERIND VAR IN K 0.001 ;[P] INTERIND VAR IN K23 0.1 ;[P] INTERIND VAR IN V2 $SIGMA 0.01 ;[P] PROPORTIONAL COMPONENT $ESTIMATION MAXEVAL=9999 PRINT=5 METHOD=1 INTERACTION NOABORT POSTHOC $COVARIANCE $TABLE ID TIME DV ETA(1) ETA(2) TVKA TVK TVK23 TVK32 TVV2 KA K K23 K32 V2 FILE=901.TAB NOPRINT