how I use function F = myfun1(x,xdata) F= @(x,xdata)​x(1).*exp(​x(2).*xdat​a);

function F = myfun1(x,xdata)

F= @(x,xdata)x(1).*exp(x(2).*xdata);

% Assume you determined xdata and ydata experimentally

xdata = [0.9 1.5 13.8 19.8 24.1 28.2 35.2 60.3 74.6 81.3];

ydata = [455.2 428.6 124.1 67.3 43.2 28.1 13.1 -0.4 -1.3 -1.5];

x0 = [100, -1]; % Starting guess

x = lsqcurvefit(@myfun1,x0,xdata,ydata);

Error: Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.

Answer 1

[Rajanya]

Hi @MUMATZ QURESHI,

The following line makes 'F' a function handle to an anonymous function-

F= @(x,xdata)x(1).*exp(x(2).*xdata);

However, 'lsqcurvefit' expects a vector of values (see here), and hence it cannot continue.

Changing the function definition of 'myfun1' to the following returns a vector of predicted values-

function F = myfun1(x,xdata)
    F = x(1).*exp(x(2).*xdata);
end

Then, the error is resolved.

xdata = [0.9 1.5 13.8 19.8 24.1 28.2 35.2 60.3 74.6 81.3];
ydata = [455.2 428.6 124.1 67.3 43.2 28.1 13.1 -0.4 -1.3 -1.5];
x0 = [100, -1]; % Starting guess
x = lsqcurvefit(@myfun1,x0,xdata,ydata);

Local minimum possible.

lsqcurvefit stopped because the final change in the sum of squares relative to 
its initial value is less than the value of the function tolerance.

x

x = 1×2

498.8309 -0.1013

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To learn more about anonymous functions and how they are used, you can refer to its documentation by executing the following command from MATLAB Command Window-

doc Anonymous Functions

Thanks!