RE: Two dependent variables

-----Original Message----- From: owner-nmusers On Behalf Of Zheng Lu Sent: Wednesday, January 31, 2007 9:11 AM To: Nick Holford Cc: nmusers Subject: Re: [NMusers] Two dependent variables Dear all: As to this kind of situation(at least two types of observations or same type of observations from at least two different assay), DO we need change our default objective function? Because I am thinking we will estimate our parameters based on multivariate normal distribution(at least bivariate normal distribution) instead of univariate normal distribution(only one type of observation), so we will have different variance across the observations and we will have covariance issue which is not zero. thanks a lot. Zheng Lu sixth-year graduate student/Smith Lab Department of pharmaceutical sciences College of Pharmacy University of Michigan 428 Church Street, Ann Arbor, MI 48109-1065 Tel: 734-763-7608(o), 734-647-1427(o), 734-647-1437(L) Fax: 734-615-6162(o), 734-763-3438(o) Quoting Nick Holford <n.holford > Hi, > > The 'FLAG' method is a trick that only works with 2 DVs. It is also a > bit inefficient because it requires that both the PK and PD prediction > are calculated but only one is used. > > A more general method uses IF THEN blocks e.g. if you have a data item > DVID with the value 1 with a conc observation and the value 2 with an > effect observation of one type and value of 3 with an effect > observation of a different type: > > CONC=F > IF (DVID.EQ.1) THEN > Y=CONC + ERR(1) > ENDIF > IF (DVID.EQ.2) THEN > Y=EMAX2*CONC/(EC502+CONC) + ERR(2) > ENDIF > IF (DVID.EQ.3) THEN > Y=EMAX3*CONC/(EC503+CONC) + ERR(2) > ENDIF > > Nick > >> >> Yes, you could do a simultaneous fitting with the same control >> stream in NM. For example you could >> have a dummy variable (Flag) that tells NM which likelihood >> function goes with which data. See below >> >> >> >> Flag 0 = PK, Flag 1=PD >> >> >> >> $ERROR >> >> Y=CONC*(1-Flag) + EFF* Flag >> >> >> >> Hopefully this would help. >> >> >> >> Best, >> >> Nidal AL-Huniti, PhD >> >> >> On 1/30/07, navin goyal <navin1180 >> >> Hello, >> I was wondering if I could model two DVs simultaneously >> with the same control stream. >> Like have to equations A=(equation) >> B= (equation) >> >> I have data for two different drugs from same patients >> Could I do it nomem ? and if yes how do I do it? >> >> Any help is appreciated, >> Thanks >> >> >> >> >> > > > > -- > Nick Holford, Dept Pharmacology & Clinical Pharmacology University of > Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand > email:n.holford > http://www.health.auckland.ac.nz/pharmacology/staff/nholford/ > > > -- The information contained in this email message may contain confidential or legally privileged information and is intended solely for the use of the named recipient(s). No confidentiality or privilege is waived or lost by any transmission error. If the reader of this message is not the intended recipient, please immediately delete the e-mail and all copies of it from your system, destroy any hard copies of it and notify the sender either by telephone or return e-mail. Any direct or indirect use, disclosure, distribution, printing, or copying of any part of this message is prohibited. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of XOMA.