Dear Tim,
Have you tried to run model 1 (with SQRT) also using $ABBREV PROTECT?
The error may occur because of a numeric error that propagates through
the SAEM steps.
Jeroen
http://pd-value.com
[email protected]
@PD_value
+31 6 23118438
-- More value out of your data!
On 05-03-2024 14:08, T. Preijers wrote:
Dear NMusers,
While running a simple 1-comp model in NONMEM using SAEM, we
discovered a warning resulting from $ERROR. Using a SQRT( **2)
describing a mixed error model resulted in zero gradients for the
additive error (see Example error model 1 below).
/*Example error model 1*/
$ERROR
IPRED = F
IRES = DV-IPRED
W = SQRT(THETA(1)**2 * IPRED**2 + THETA(2)**2)
IF (W.EQ.0) W = 1
IWRES = IRES/W
Y = IPRED+W*ERR(1)
However, when simplifying the $ERROR code omitting the use of SQRT()
and THETA(x)**2 (see Example error model 2 below), a successful SAEM
run was obtained.
/*Example error model 2*/
$ERROR
IPRED = F
IRES = DV-IPRED
W = THETA(1) * IPRED + THETA(2)
IF (W.EQ.0) W = 1
IWRES = IRES/W
Y = IPRED + W*ERR(1)
Initial values for both THETAs were positive (TH1: 0.417, TH2: 0.545)
and constrained with a lower boundary of 0. Moreover, the expected
values for IPRED were ranged from 1-700 mg/L.
Our interest lies in what has driven this error. Perhaps someone else
has encountered this before?
Looking forward to receiving any answers/comments!
Kind regards,
*Dr. T. Preijers, PharmD, PhD*
/Hospital Pharmacist and Clinical Pharmacologist/
Hospital Pharmacy Erasmus MC Rotterdam The Netherlands
Rotterdam Clinical Pharmacometrics Group
