$COV

From: "Emily" Subject: [NMusers] $COV Date: Wed, 1 May 2002 12:08:12 +0800 Dear NONMEM users: I'm working on a nonlear model, and the $COV step can't work. Here is my control file: $PROB A $INPUT ID AGE SEX HT WT EVID TIME AMT SS II DV MDV $DATA data $SUBR ADVAN6 TOL=3 $MODEL COMP=(DEPOT, DEFDOS), COMP=(CENTRAL, DEFOBS) $PK TVVM=THETA(1) TVKM=THETA(2) VM=TVVM*(1+ETA(1)) KM=TVKM*(1+ETA(2)) K12=THETA(3) V2=THETA(4) $DES C2=A(2)/V2 DADT(1)=-K12*A(1) DADT(2)=K12*A(1)-VM*C2/(KM+C2) $ERROR Y=F+ERR(1) $THETA (0,40); 1 VM (0,4); 2 KM (0,0.6); 3 K12 (0,50); 4 V2 $OMEGA 0.01, 0.01 $SIGMA 40 $EST NOABORT PRINT=1 $TABLE ID AMT DV $COVARIANCE $SCATTER PRED VS DV UNIT $SCATTER RES VS WT The $COV step yeild follwing message: R MATRIX ALGORITHMICALLY SINGULAR COVARIANCE MATRIX UNOBTAINABLE Can anyone give me any suggestion, please? Thanks a lot !! Emily