Meenu - you appear to be using the WNL classic engine, and probably your data is insufficient for the WNL classic engine to work out it’s own initial esitmates. have any of you subjects fitted? if so simply use their final estimates as initial estimates for the other subjects.
Thank you Dr Serge and Dr Simon! I could run it finally after sorting by “patient ID”. But I am getting different condition numbers for each patient’s PK parameters. How can I compare between different models? I am currently trying 1 compartment extravascular. Which condition number will I use to compare between models? In the diagnostics section, again I am getiing values for each patient. How do i compare between models for the best fit?
Meenu, If you are modelling the data as individuals, I would probably look at comparing summaries of AIC (or SBC), remembering that lower numbers are better, when comparing the nested models on the SAME data.
However you should also be considering the plot as well as precision of parameters obtained (ie. CV%) as well as the planned use of the model for future simulations etc.
If you can post the project we can perhaps make some more specific suggestions.
I would suggest to switch to Phoenix NLME model, Naive Pooled engine could be used with WNL license. Then you can select exactly the same model (see the NLME User’s guide, ‘An example of individual modeling with Phoenix model’, but you need to switch to population mode). Create another model object(s) and Model Comparer object too.
Regarding diagnostics: no simple answer. Try this one: