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Re: NONMEM code for Mixture Model

From: Huali Wu <hualiw>
Date: Fri, 13 Mar 2009 09:48:52 -0400

Hi Nidal,

Thank you for your help. I searched the NONMEM user guides and finally =
found an example of mixture model. It is on part VIII, page 456. I have =
tried the codes and it works for my model. It improved the fitting but I =
noticed some of IWRES increased dramatically. I am trying to figure out =
why.

Thanks again,

Best regards,

Huali

----- Original Message -----
  From: nidal.alhuniti
  To: Huali Wu
  Cc: nmusers
  Sent: Thursday, March 12, 2009 3:44 PM
  Subject: Re: [NMusers] NONMEM code for Mixture Model


  Hi Huali,

  You could use $MIX. Please see the NM help files for $MIX. You have to =
specify the number of populations (in your case 2) so



  $MIX

      NSPOP=2

      P(1)=THETA(4)

      P(2)=1.-THETA(4)



  Then use

  EST= MIXEST



  Hopefully this helps.

  Best,

  Nidal



  Nidal AL-Huniti, PhD

  Associate Director, Modeling and Simulations

  ICON Development Solutions SM




  On 3/12/09, Huali Wu <hualiw
    Dear NMusers:

    I am working on dataset with high variability on clearance and =
patients in different disease states seems have different distribution =
of clearance. So I want to try the mixture model but I don't know how to =
do the coding. I listed the code of my base model as below:

    $PROB 1hr IV INFUSION SINGLE DOSE WITHOUT COVARIATES
    $DATA data01.CSV IGNORE=C
    $INPUT ID TIME DV AMT RATE MDV

    $SUBROUTINES ADVAN9 TRANS1 TOL=5
    $MODEL NPAR=3, NCOMP=1, COMP=(CENTRAL,DEFOBS)

    $PK
             V1 = THETA(1)*EXP(ETA(1))
             VM = THETA(2)*EXP(ETA(2))
             KM = THETA(3)
            
              S1 = V1
           

    $ERROR

    Y=F+F*EPS(1)+EPS(2)

    IPRED=F
    IRES=DV-IPRED
    IF(AMT.NE.0)W=1
    IF(AMT.EQ.0)W=F
    IWRES=IRES/W

    $DES
           C1 = A(1)/V1
           DADT(1) = - C1*VM/(KM+C1)
                              

    $THETA (0, 4.47) (0, 155) (0, 1380)
    $OMEGA BLOCK (2)
    0.5
    0.3 0.9

    $SIGMA (0.01) (0.1)

    $EST POSTHOC METHOD=1 MAXEVAL=9990 PRINT=5
    $COV
    $TABLE ID TIME DV AMT RATE V1 VM KM IWRES IPRED NOPRINT =
FILE=TAB4 ONEHEADER
    $SCAT (RES WRES) VS TIME BY ID

    Any suggestion will be highly appreciated!

    Best regards,

    Huali

     


Received on Fri Mar 13 2009 - 09:48:52 EDT

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