MATLAB: Failure in initial objective function evaluation. FMINUNC cannot continue.

optimization

I tried to evaluate this function but I am getting this error Failure in initial objective function evaluation.
FMINUNC cannot continue.
Please what is the best way to evaluate this function
f = x(2)^2*x(9)^2 + x(2)^2*x(9) + x(2)^3*x(9) - x(3)*x(5)*x(9)^2 + x(6)*x(8)*x(9)^2 + x(6)*x(8)*x(9)^3 + x(2)*x(6)*x(8)*x(9)^2;

Best Answer

Unless it is already in a function file, it needs to be an anonymous function: 
f = @(x) x(2)^2*x(9)^2 + x(2)^2*x(9) + x(2)^3*x(9) - x(3)*x(5)*x(9)^2 + x(6)*x(8)*x(9)^2 + x(6)*x(8)*x(9)^3 + x(2)*x(6)*x(8)*x(9)^2;
If it is in a function file (and you have passed the function handle to fminunc correctly), the initial parameter estimates could be the problem. Please post those.
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