RE: Error models and weighting
From: "Gibiansky, Leonid" <gibianskyl@globomax.com>
Subject: RE: Error models and weighting
Date: Thu, 24 May 2001 08:02:25 -0400
> In a previous message via nmusers, Leonid Gibiansky suggested that I use
> a simplier model - e.g. Y = F*(1+EPS(1))+EPS(2). If this model is
> used, I do not know how to get IWRES for using Xpose.
IWRES=(DV-IPRED)/SQRT(F*F*OMEGA1+OMEGA2)
where OMEGA1 and OMEGA2 are the variances of EPS(1) and EPS(2). To get them "on the fly" during the NONMEM run you would need to rewrite the code above as
$ERROR
Y = F*(1+THETA(1)*EPS(1))+THETA(2)*EPS(2)
fix the variances of EPS(1) and EPS(2) to 1
$SIGMA
1 FIX
1 FIX
and then
IWRES=(DV-IPRED)/SQRT(F*F*THETA(1)*THETA(1)+THETA(2)*THETA(2) )
Leonid