Additive residual error
Hi, NM users:
I have a typical 2-compartment model that can describe my data quite well,
except the final gradient for the additive residual error is '0'. I
therefore fix the additive residual error to '0', but then NM would not
run. I tried different initial estimations for other parameters but the
additive residual error seems to be the one that decide whether NM will
run. Can anyone tell me why this would happen and how to solve it?
Thank you very much in advance for your help.
Siwei