lsqcurvefit Error using /

Question

Chris Andoh 2019-8-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476551-lsqcurvefit-error-using

编辑： Chris Andoh 2019-8-18

Hi, I'm trying to use MATLAB to fit some data using nonlinear least square fitting. When I run my code:

xdata = NbO2_219_T';        %NbO2_219_T is a column vector (want a row vector)
ydata = NbO2_219_ln_rho';   %NbO2_219_ln_rho is a column vector
fun = @(x,xdata) (x(1)*(1 + (sqrt(1 + xdata./x(2)) - 1)/(xdata./x(2))))/sqrt((sqrt(1 + xdata./x(2)) - 1)) + x(3);   
                                                          %x = [x(1) x(2) x(3)] Parameters to solve for
x0 = [5 7e-3 -30];                                        %Initial geusses for parameters
x = lsqcurvefit(fun,x0,xdata,ydata)

I get the following error:

Error using /

Matrix dimensions must agree.

Error in

nonlinearfit_rho_vs_T>@(x,xdata)(x(1)*(1+(sqrt(1+xdata/x(2))-1)/(xdata/x(2))))/sqrt((sqrt(1+xdata/x(2))-1))+x(3)

Error in lsqcurvefit (line 213)

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

Error in nonlinearfit_rho_vs_T (line 14)

x = lsqcurvefit(fun,x0,xdata,ydata)

Caused by:

Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.

Does anyone know what could be the potential cause of this? I tried replacing the '/' with './' but unfortunately it did not solve the issue.

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Answer 1

Stephen23 2019-8-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476551-lsqcurvefit-error-using#answer_388041

编辑：Stephen23 2019-8-18

在 MATLAB Online 中打开

Replacing both of the mrdivide operators with rdivide operators gets rid of the error:

>> fun = @(x,xd) (x(1)*(1+(sqrt(1+xd./x(2))-1)./(xd./x(2))))./sqrt((sqrt(1+xd./x(2))-1))+x(3);
>> xdata = randi(9,1,7);
>> x0 = [5,7e-3,-30];
>> fun(x0,xdata(:))
ans =
  -28.376
  -28.678
  -28.914
  -28.376
  -28.376
  -28.979
  -29.029