MATLAB: Nonlinear data fitting for a system of ODE using lsqcurvefit (finding unknown parameters)

curve fittingdifferential equationsodeoptimizationparameter estimationsolvesystem of ode

I have a set of experimental data in staedy state condtion(without time dependent). This experiment has been done at 4 different concentration including 3 compounds. the values of concentration at inlet(x=0) and outlet(x=1) are known. i used ODE15s to solve the differenial equations and find the values at outlet and then compare them with real values to find the unknown kinitic parameters(i followed https://www.mathworks.com/matlabcentral/answers/43439-monod-kinetics-and-curve-fitting#comment_89455). but when i ran the code i got some error as below: Not enough input arguments.

Error in Untitled10>objfun (line 25)
[tSol,YSol]=ode15s(@diffeq,x,Z);
Error in lsqcurvefit (line 202)
            initVals.F = feval(funfcn_x_xdata{3},xCurrent,XDATA,varargin{:});
Error in Untitled10 (line 20)
[kfit,Rsdnrm,Rsd,ExFlg,OptmInfo,Lmda,Jmat]=lsqcurvefit(@objfun,K,Cin,yy)
Caused by:
    Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.

Best Answer

[kfit,Rsdnrm,Rsd,ExFlg,OptmInfo,Lmda,Jmat]=lsqcurvefit(@(K) objfun(K,Y0,x),K,Cin,yy)

Related Solutions

MATLAB: Fitting the solution of odes to data using fmincon with nonlinear restraints

You are using

 [K1,fval,exitflag,output]=fmincon(@ssq,K0,[],[],[],[],lb,ub,@dissoc);

That is going to call ssq with a single parameter that is a vector. Your ssq function expects three inputs and will fail if it attempts to access the second or third inputs as those are missing.

http://www.mathworks.com/help/matlab/math/parameterizing-functions.html

MATLAB: The entries in tspan must strictly increase or decrease.

You have

[k,Rsdnrm,Rsd,ExFlg,OptmInfo,Lmda,Jmat]=lsqcurvefit(@IntegratedModel,k0,c,t);

k0 is being passed in the x0 position -- an initial guess at the parameters to be found.

c is being passed in the xdata position.

t is being passed in the ydata position.

lsqcurvefit will then call IntegratedModel passing in "a vector or matrix x, and a vector or matrix xdata". Here, x would refer to the trial parameter whose effect is to be calculated at the positions given by xdata.

You are receiving the values in IntegratedModel under the names k and t. k is consistent with your naming use of passing in k0 and expecting k to be output. However, the second position is having xdata passed in, and your xdata is your c matrix, a 3 x 7 matrix which is not in numeric ascending or descending order.

In IntegratedModel you attempt to pass this "t" in to ode45 as if it were tspan values... but it isn't.

Perhaps your code should have been

    [k,Rsdnrm,Rsd,ExFlg,OptmInfo,Lmda,Jmat]=lsqcurvefit(@IntegratedModel,k0,t,c);

Best Answer

Related Solutions

MATLAB: Fitting the solution of odes to data using fmincon with nonlinear restraints

MATLAB: The entries in tspan must strictly increase or decrease.

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