How to check the internal solution results of Fsolve to know where the matrix dimension assignment has problem?

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farzad 2019-10-30

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https://ww2.mathworks.cn/matlabcentral/answers/488316-how-to-check-the-internal-solution-results-of-fsolve-to-know-where-the-matrix-dimension-assignment-h

编辑： Matt J 2019-10-30

Hi All

I am solving a set of 2nd order equations via fsolve. But it seems like that already in the first equation I have got a problem. and I get the following error. the fsolve was working on a previous set of equations. but now just having change some parameters, I see the following error.

I need to know if there is any way to monitor the real time solution results to see where this problem arises? I see that even x is not defined here yet, since this error comes before.

In an assignment  A(:) = B, the number of elements in A and B must be the same.
Error in root2d (line 30)
F(1) = my equation;
Error in fsolve (line 230)
            fuser = feval(funfcn{3},x,varargin{:});
Error in Fsolver (line 167)
        [x,fval,exitflag,output] = fsolve(fun,x0init,options);
Caused by:
    Failure in initial objective function evaluation. FSOLVE cannot continue.

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Answer 1

Matt J 2019-10-30

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https://ww2.mathworks.cn/matlabcentral/answers/488316-how-to-check-the-internal-solution-results-of-fsolve-to-know-where-the-matrix-dimension-assignment-h#answer_398985

编辑：Matt J 2019-10-30

在 MATLAB Online 中打开

Yes, if you re-run your code after executing

>> dbstop if caught error

at the command line, the code will pause execution at the point which triggered your error. If needed, you can also navigate to the workspace of other functions in the chain of function calls that caused the error using the Function Call Stack dropdown: