Trying to do a non linear fit under non linear constraints using lsqcurvefit: constraint needs more input

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Asheesh 2023-6-5

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https://ww2.mathworks.cn/matlabcentral/answers/1978379-trying-to-do-a-non-linear-fit-under-non-linear-constraints-using-lsqcurvefit-constraint-needs-more

编辑： Matt J 2023-6-5

I am trying to do a non linear fit under non linear constraints using lsqcurvefit.

the objective function looks like this: obj=@(x,xdata) (calculations using x(1), x(2),x(3),xdata)

the non linear constraint condition has the form K=@(x,xdata,ydata,otherdata1) (calculations using x(1),x(2),x(3),xdata,ydata,otherdata1)

the nlcon (constraint argument) in lsqcurvefit takes only x as input (so to be able to pass K to nlcon, i have created a wrapper so that the K_wrapper facilitates passing the extra arguments into nlcon)

it should have the form:

function [c,ceq]=nlcon(x)

c=[]

ceq=K_wrapper

end

i ran nlcon separately and it works, which would mean that the wrapper functions work

i ran lsqcurvefit without the constraint condition and it works

The problem: as soon as i couple constraint and lsqcurvefit together, i get an error saying that

"Error using TopLevelScript>@(x,xdata) obj(x,xdata)

Too many input arguments.

Error in lsqcurvefit (line 225)

initVals.F = feval(funfcn_x_xdata{3},xCurrent,XDATA,varargin{:});

Error in TopLevelScript (line 45)

res=lsqcurvefit(obj,x0,xdata,ydata,lb,ub,A,b,Aeq,beq,nlcon);

Caused by:

Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.

how should i resilve this?

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Asheesh 2023-6-5

编辑：Matt J 2023-6-5

在 MATLAB Online 中打开

sorry about that, here is the code:

%%newTOplevelScript
load("data.mat")
%%
%%introduce the vectors after loading data
s=s_data(6:end-2); %xdata
a=a_data(6:end-2); %ydata
%%
%define FitFunctionWrapper
Fit = @(params,scattVect,absInt) (a-params(1).*s.^-4- ...
    params(2).*s.^2-params(3));
FitFunctionWrapper = @(params,s) Fit(params,s, ...
    a);
sigma=1.6;
%% 
%%
%define nlcon 
pass_on_wrapper = @(s,a,sigma,params) (calculate_sec_der ...
    (s,a,sigma,params(1),params(2),params(3)));
transfer_wrapper = @(params) (pass_on_wrapper(s,a,sigma,params));
nlcon_wrapper = @(params) (transfer_wrapper(params));
%% initialize x0
initial_P=0.1;
initial_C1=100;
initial_C2=1;
x0=[initial_P,initial_C1,initial_C2];
%% other arguments for lsqcurvefit
A=[];
b=[];
Aeq=[];
beq=[];
lb=zeros(size(x0));
ub=200*(x0); %maybe adjust it a little more
%%perform lsqcurvfit
zz=nlcon_wrapper(x0);
result=lsqcurvefit(FitFunctionWrapper,x0,s,a,lb,ub,A,b, ...
    Aeq,beq,nlcon_wrapper);
%%here, calculat_sec_der(s,a,sigma,params) = 0 is the non linear constraint condition
%%Fitfunction is the objective  function and takes params and s as input
%% s and a are 760x1 sized doubles
%% zz gets executed properly, result=lsqcurvefit(FitFunctionWrapper,x0,s,a); also works
%% result=lsqcurvefit(FitFunctionWrapper,x0,s,a,lb,ub,A,b,Aeq,beq,nlcon_wrapper); gives the following error: