Could you show the code and the data sample?
It is possible that urine compartment does not have SS, as it does not
have elimination. It needs to be emptied time to time, and it could be
difficult to code SS of this system. To check, you may look on the urine
compartment concentrations with additional doses: do they converge to SS
to increase with time?
Leonid
On 7/9/2024 2:41 PM, Abdelrahman Saqr wrote:
Dear Colleagues,
I am encountering the following error when I run a model that includes
plasma and urine data and SS data column =1.
When I remove the urine data (modelling only the plasma data), the model
runs without any error.
When I drop the SS column (run a single dose or even with additional
doses), the model runs without any error.
When I have both the urine data and SS assigned as 1 or 3, I face the
following error :
MONITORING OF SEARCH:
0THE INPUT MATRIX IS SINGULAR. SOME OF THE DIAGONAL ELEMENTS OF THE UPPER
TRIANGULAR MATRIX U OF THE LU FACTORIZATION ARE CLOSE TO ZERO.
0THE INPUT MATRIX IS SINGULAR. SOME OF THE DIAGONAL ELEMENTS OF THE UPPER
TRIANGULAR MATRIX U OF THE LU FACTORIZATION ARE CLOSE TO ZERO.
0PRED EXIT CODE = 1
0INDIVIDUAL NO. 1 ID= 3.00200000000000E+03 (WITHIN-INDIVIDUAL)
DATA REC NO. 1
THETA=
8.60E+00 1.39E+01 1.78E+02 1.33E-01 1.00E+00
OCCURS DURING SEARCH FOR ETA AT INITIAL VALUE, ETA=0
NUMERICAL DIFFICULTIES WITH INITIAL ESTIMATE OF STEADY-STATE SOLUTION.
DA MATRIX IS NOT INVERTIBLE AT A ZERO STATE VECTOR.
TRY SETTING INITIAL ESTIMATE USING SS=3.
I appreciate your help with interpreting and fixing this error.
Thanks,
--
*Abdelrahman Saqr *
MS. Experimental and Clinical Pharmacology | University of Minnesota
PhD Candidate | Department ofExperimental and Clinical Pharmacology
College of Pharmacy | University of Minnesota
www.linkedin.com/in/abdelrahman-saqr
<http://www.linkedin.com/in/abdelrahman-saqr>
