Hi Penny,
I suspect you are right in your conclusion that number of records for each id
matters in this case.
My solution to your problem would be to add columns for IIV to your dataset
outside of NONMEM.
Quite easily done in R.
Use the rmvnorm R function to simulate your etas, 600 rows times as many etas
you have
require(mvtnorm)
sigma<-diag(c(1,2,3)) ## example 3 etas , without block, variances 1,2 and 3
Etas<-rmvnorm(600,sigma=sigma)
colnames(Etas)<-paste("ETAr",1:ncol(Etas),sep="")
Then load your NONMEM datafile as is now with dosing and observational records,
d0<-read.table(.....)
Match each of the rows in Etas to ID in your data
Etas2<-Etas[as.numeric(factor(d0$ID)),]
and then append the simulated etas
d1<-cbind(d0,Etas2)
and then finaly save the d1 R data.frame as a text file using write.table.
In your nonmem code you the just replace eta(1) with ETAR1, and so on.
BW
Magnus Åstrand
Principal Clinical Pharmacometrician, Ph.D.
_____________________________________________________________________________________________
AstraZeneca
Innovative Medicines | Quantitative Clinical Pharmacology
SE-431 83 Mölndal, Sweden
T: +46 (0)31 776 23 41
Mob: +46 (0)708 467 667
magnus.astr...@astrazeneca.com
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From: owner-nmus...@globomaxnm.com [mailto:owner-nmus...@globomaxnm.com] On
Behalf Of Zhu, Penny
Sent: den 9 mars 2017 19:19
To: nmusers@globomaxnm.com
Subject: [NMusers] question about random seed for simulation
Dear All
I have finished a multiple dose simulation for 600 subjects and want to perform
a single dose simulation (different sampling time) on the same subjects (same
ETA as the first simulation). I used the same seed for the simulation step, it
turned out the first subject was the same and the rest of the subjects are not
and I am not sure whether this was due to the fact that the two simulation has
different number TIME records. If so, I wonder what is the proper way to set
the simulation seed so that the ETAs for the second simulation will be
identical to the first one.
I know that I could output the individual parameter estimate from the first
simulation and import them into the second one. But I was thinking if the
random seed can be synchronized between the two simulation, it could be an
easier solution.
Your help is very much appreciated!
Thank you very much and best regards!
Penny (Peijuan) Zhu, Ph.D.
Associate Director Clinical Pharmacology
Cell: 862-926-9079
PD Bio-Pharma CDMA
Sandoz
1N025, 100 College Road West
Princeton, NJ 08540
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