How to fit differential equations system with isqcurvefit when Function value and YDATA sizes are not equal.

Hi! I have a system of 13 differential equations that represents a pharmacokinetics in 13 different organs (compartiments) and I want to fit them with my experimental data, however I only have experimental concentrations at different times for two organs. I want to learn how to use isqcurvefit when Function value and YDATA sizes are not equal. Is that possible?

Thanks in advance

[Torsten]

Only select the simulated values for the two organs at the times where you have experimental Ydata in the process of parameter estimation.

[María Elena Bravo-Gómez]

Thank you very much Torsten!, It works!. It took me a few days to understand what you were referring to because I am actually very new to this. But finally I got it and it works, thank you very much. Your recommendation made me look for how to call the variables and I managed to put together what I wanted.