Fit an Ordinary Differential Equation (ODE) using lsqcurvefit

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Jonas Hilpert
Jonas Hilpert 2018-11-14
评论： Torsten 2018-11-15
Hello,
i have a system of 11 ODE's (ode45) and want to fit them to measured data. For that i have 11 variables i want to optimate. My Question:
Additional to the lb and ub in the lsqcurvefot solver, i want a condition for the variables like x(1)+x(2)=5. Is that possible?

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Torsten
Torsten 2018-11-14
编辑：Torsten 2018-11-14
Remove parameters x(1) and x(2) from your list and introduce one new variable x(12). From x(12), calculate x1=5*cos^2(x(12)) and x2=5*sin^2(x(12)) and insert x1 and x2 instead of x(1) and x(2) in your ODE system.
If your constraints are more complicated than this one, use "fmincon" instead of "lsqcurvefit".
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Jonas Hilpert
Jonas Hilpert 2018-11-15
thank you very much for your answer! You are right, my constraints are more complicated. Actually i need as follows: x(1)+x(2)+x(3)+x(4)+x(5)+x(6) = 5 or probably even more constraints.....
I have tried your suggestion, unfortunately this is not working really well. I was thinking "fmincon" is not working for a system of ode's, or am I wrong? I hope you have another suggestion for me
Torsten
Torsten 2018-11-15
"lsqcurvefit" has nothing to do with the integration of the system of ODEs. That's why "fmincon" will work as well as "lsqcurvefit".

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