$PROBLEM    2 compartment fitting
$INPUT       ID TIME AMT DV WTKG GENDER AGE DROP
$DATA      {data_dir}/dataExample1.csv IGNORE=@
           
$SUBROUTINE ADVAN4
$ABBR DERIV2=NO
$PK      
  CWTKG = WTKG/70  ;; CENTERED ON ONE 
  CAGE = AGE/40
  TVV2=THETA(2) 
  V2=TVV2*EXP(ETA(4)) 
  TVCL= THETA(1)  
  CL=TVCL*EXP(ETA(3)) 
  K=CL/V2  
  TVKA=THETA(3) 
  KA=TVKA  {KAETA[1]}  
  S2 	= V2/1000 
  {ALAG[1]}
  K23=THETA(4)*EXP(ETA(1))
  K32 = THETA(5)*EXP(ETA(2))
$ERROR     
 REP = IREP      
 IPRED =F  
 IOBS = F*EXP(EPS(1)) + EPS(2)
 Y=IOBS
$THETA  ;; must be one THETA per line.
 (0.001,100)	; THETA(1) CL UNITS =  L/HR
 (0.001,500) 	; THETA(2) V  UNITS = L
 (0.001,2) 	; THETA(3) KA UNITS = 1/HR  
 (0,0.1)	; THETA(4) k23
 (0,0.1)	; THETA(5) k32
  
 {ALAG[2]} 
 
$OMEGA   
  0.6  	 ; ETA(1) K23
  0.5  	; ETA(2) K32
$OMEGA   ;; search band
  0.4   ; ETA(3) CLEARANCE
  0.3  	; ETA(4) VOLUME
{KAETA[2]}   

  
$SIGMA   
0.1
10 
 
  
$EST METHOD=COND INTER MAX = 9999 MSFO=MSF1 
$COV UNCOND PRINT=E