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Re: a question about the mixture distribution

From: wu kehua <zckehua>
Date: Tue, 17 Nov 2009 14:19:34 -0600

Dear Joseph,

Sorry for so delayed response. I build the model as your recommendations,
and the model works very well.

But there is another problem when the number of subgroups scales up to 12.
PDx-pop shows a problem with my model: "332 $MIX: NSPOP OR INDEX I OF P(I)
EXCEEDS CONSTANT "MMX" IN SIZES. "
It seems that I should change the value of 'MMX'. I searched at the help
files and did not find how to change it.

I appreciate your and your colleagues' help.

Best regards,

Kehua

2009/10/20 Joseph Standing <joseph.standing

> Dear Kehua,
>
>
>
> We discussed your question in the Uppsala pharmacometrics meeting
> yesterday. If I understood your original question correctly, it was that
> there were two possible conditions for ALPHA and BASE, and that each
> combination was possible. A general principle for coding this:
>
>
>
> .
>
> $MIX
>
>
>
> P(1) = Theta(alph) * Theta(Base)
>
> P(2) = (1 Theta(alph)) * Theta(Base)
>
> P(3) = Theta(alph) * (1 - Theta(base))
>
> P(4) = (1 Theta(alph)) * (1-Theta(base)) ; = 1 P(1=
) P(2)
> P(3)
>
>
>
>
>
>
>
> $THETA (0,x,1) ; Theta(alph)
>
> $THETA (0,y,1) ; Theta(base)
>
>
>
>
>
> You should be able to extend this general principle to suit your specific
> case.
>
> Best wishes,
>
>
>
> Joe Standing
>
>
> ------------------------------
>
> *From:* owner-nmusers
]
> *On Behalf Of *Fidler,Matt,FORT WORTH,R&D
> *Sent:* den 13 oktober 2009 21:33
> *To:* wu kehua
> *Cc:* nmusers
> *Subject:* RE: [NMusers] a question about the mixture distribution
>
>
>
> Kehua,
>
>
>
> The number of subgroups depend on how you view the subgroups.
>
>
>
> There are three subgroups for ALPH, and there are two subgroups for BASE.
> Therefore, there could be
>
>
>
> 3*2 = 6 subgroups
>
>
>
> or
>
>
>
> 3+2 = 5 subgroups -- 3 for ALPH and 2 for BASE.
>
>
>
>
>
> While technically there are 6 groups, you only code for 5, and each of
> these five have sufficient information to determine which group each
> individual is a member of.
>
>
>
> Matt.
>
>
>
>
> ------------------------------
>
> *From:* wu kehua [mailto:zckehua
> *Sent:* Tuesday, October 13, 2009 11:58 AM
> *To:* Fidler,Matt,FORT WORTH,R&D
> *Cc:* nmusers
> *Subject:* Re: [NMusers] a question about the mixture distribution
>
> Hi Matt,
>
> Thank you very much for your kindly reply. It is very helpful.
>
> I still have another question about this issue. I have tried the first
> option. I applied three subgroups on ALPH and two subgroups on BASE. I th=
ink
> there should be six subgroups in total, right? But in the resulting data,
> there are just five subgroups. The code follows,
>
> $PRED
>
> CALLFL =1
> EST = MIXEST
> IF (MIXNUM.EQ.3) THEN
> ALPH = (THETA(3))
> END IF
> IF (MIXNUM.EQ.2) THEN
> ALPH = (THETA(2))
> END IF
> IF (MIXNUM.EQ.1) THEN
> ALPH = (THETA(1))
> ENDIF
>
>
> IF (MIXNUM.EQ.4) THEN
> BASE=THETA(4)
> ELSE
> BASE=THETA(5)
> END IF
>
>
>
> $MIX
>
> P(1) = THETA(6)
> P(2)=THETA(7)
> P(3) = 1-THETA(7)-THETA(6)
> P(4)=THETA(8)
> P(5)=1-THETA(8)
> NSPOP = 5
>
> Sorry to bother you and thank you very much. I will try that one mentione=
d
> in your mail and let you know the results.
> I appreciate your helps.
>
> Best regards,
>
> Kehua
>
> 2009/10/13 Fidler,Matt,FORT WORTH,R&D <Matt.Fidler
>
> Kehua,
>
>
>
> Option 1 is definitely better. This states that there is a possibility
> that a population falls into ALPH1 or ALPH2. Within that same population
> there are two populations for BASE.
>
>
>
> The other option states that each person in the has distinct parameters
> that four populations fall into: ALPH - Pop1, ALPH - Pop 2, Base -Pop 1, =
or
> Base -Pop2. Therefore, if you selected ALPH - pop1, you wouldn't have th=
e
> parameter base. (You require this by having P1 - P4 to add up to be one -
> the total probability).
>
>
>
> A third option you may consider is if you have reason to believe that the
> populations that have ALPH1 and Base1 are the same:
>
>
>
> $PRED
> IF (MIXNUM.EQ.2) THEN
> ALPH =THETA(1)
>
> ELSE
> ALPH = THETA(2)
> ENDIF
>
> IF (MIXNUM.EQ.2) THEN
>
>
> BASE=THETA(3)
> ELSE
> BASE=THETA(4)
> END IF
>
> $MIX
>
> P(1) = THETA(5)
> P(2) = 1-THETA(5)
>
> NSPOP = 2
>
>
>
> I haven't run anything like Option 1, and am unsure if NONMEM supports tw=
o
> separate populations for ALPH and BASE. Has anyone tried this?
>
>
>
> Matt.
>
>
> ------------------------------
>
> *From:* owner-nmusers
]
> *On Behalf Of *wu kehua
> *Sent:* Tuesday, October 13, 2009 10:58 AM
> *To:* nmusers
> *Subject:* [NMusers] a question about the mixture distribution
>
> Hi,
>
> I am a new NONMEM user. I have a question about mixture distribution.
>
> I have two parameters. How to apply mixture distribution on the both
> parameters? I should use the first one or the second one?
>
> *First,*
> $PRED
> IF (MIXNUM.EQ.2) THEN
> ALPH =THETA(1)
> END IF
> IF (MIXNUM.EQ.1) THEN
> ALPH = THETA(2)
> ENDIF
>
> IF (MIXNUM.EQ.3) THEN
> BASE=THETA(3)
> ELSE
> BASE=THETA(4)
> END IF
>
> $MIX
>
> P(1) = THETA(5)
> P(2) = 1-THETA(5)
> P(3)=THETA(6)
> P(4)=1-THETA6)
> NSPOP = 4
>
>
> *Second,*
>
> IF (MIXNUM.EQ.1) THEN
> ALPH =THETA(1)
> BASE=THETA(3)
> END IF
> IF (MIXNUM.EQ.2) THEN
> ALPH = THETA(1)
> BASE=THETA(4)
> ENDIF
> IF (MIXNUM.EQ.3) THEN
> ALPH = THETA(2)
> BASE=THETA(3)
> ELSE
> ALPH = THETA(2)
> BASE=THETA(4)
> END IF
>
> $MIX
>
> P(1) = THETA(5)
> P(2) = THETA(6)
> P(3)=THETA(7)
> P(4)=1-THETA(5)-THETA(6)-THETA(7)
> NSPOP = 4
>
> Thank you very much!
>
> Best regards,
>
> Kehua
>
>
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Received on Tue Nov 17 2009 - 15:19:34 EST

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