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