Thanks for the explanation on selecting reasonable initial estimates for epsilon. I understand how to choose the estimates for additive and multiplicative error models, but it is not clear what to use for other error models (i.e., CmixRatio, power, etc.). If you could provide examples for these other error models that would be helpful.
Unfortunately, I cannot share the project file due to confidentiality, but I can describe the issues in more detail (using NLME v1.0):
I did not have a problem using the FOCE-LB engine with the additive error model. However, it does not appear to be an appropriate error model. I copied the file and evaluated the multiplicative error model with a reasonable initial estimate (stdev=0.5). FOCE-LB provided estimates with stderr, but the return code was -1, indicating an error with the convergence. When I tried other engines, an error message appeared. Only using the FO engine was I able to get estimates with stderr and a retcode=1. However my understanding is that the FO method is generally not recommended for final estimates. Any advice on how to use the FOCE-LB or FOCE-ELS methods to get an acceptable return code? Also, when comparing different error models, is it recommended to use the same engine? I also explored the CmixRatio error model but it is not clear to me what to enter for the initial estimate for epsilon. In this case the output contains parameter estimates but no stderr.
Many thanks for your advice and help!