Dear Sean,

Thanks for your information. Here are some of the error messages:

• NDSolve::indexss: The DAE solver failed at t = 29.010538367426943`. The solver is intended for index 1 DAE systems and structural analysis indicates that the DAE is structurally singular. >>
• InterpolatingFunction::dmval: Input value {30.} lies outside the range of data in the interpolating function. Extrapolation will be used. >>
• General::stop: Further output of InterpolatingFunction::dmval will be suppressed during this calculation. >>
• General::stop: Further output of InterpolatingFunction::dmval will be suppressed during this calculation. >>
• General::stop: Further output of NDSolve::nderr will be suppressed during this calculation. >>

I think the error messages are related to the below command:

The command is being used to solve the 1st order different equation of those parameters. Parameters s1i, s2i, etc are given as initial parameters. The main purpose of this script is to obtain estimated parameters a11e, a12e, a21e, etc. by using FindFit command. I cant get the end results because I already got those error messages half way.

Here is the same script as attached before to show the initial part of the script to the part when I got the error messages (FindFit script.nb). So far I still cant figure out what went wrong why I got those error messages. So I would like to know how to interpret those error messages to find out which parts are wrong whether it may relate to the input data or to the command itself.

Hence I am looking forward to have further advise from you. Thanks a lot in advance.

Best Regards, Intan

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