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fmin additional variables ( are vector)

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Hello
I am trying to use fmincon but add extra parameters to the function. The function is
function sw = opt(x,g_14,k_4)
sw = ((log(1+x(1))*log(1+x(1)))+log(1+x(1)).*g_14 + k_4)/(1.6806) + ((log(1+x(2))*log(1+x(2))).*g_14 + ((log(1+x(3))*log(1+x(3))).*g_14 ;
end
where g_14 is a numeric vector that change. The system is
x0 = [0,0,0];
A = [1 -1 0;
0 1 -1;
1 0 -1];
b = [0 0 0];
Aeq = [176.9880 179.0538 296.3700];
beq = [1225];
lb = [0 0 0];
up = [Inf Inf Inf];
And finally; [X fval exitflag output lambda grad hessian] = fmincon(@(x) fun(x,g_14,k_4) , x0, A, b, Aeq, beq,lb, up);
When i run the code , MATLAB returns : Supplied objective function must return a scalar value.
So, I try change objetive function and solution by
  • [X fval exitflag output lambda grad hessian] = fmincon(fun, x0, A, b, Aeq, beq,lb, up);
  • function sw = opt(x)
sw = ((log(1+x(1))*log(1+x(1)))+log(1+x(1)).*g_14 + k_4)/(1.6806) ((log(1+x(2))*log(1+x(2))).*g_14 + ((log(1+x(3))*log(1+x(3))).*g_14 ;;
end
So in this case , the problem is ; Undefined function or variable 'g_14'. , even though I had already defined them on the outside
Thanks !!

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Accepted Answer

Thiago Henrique Gomes Lobato
Your first attempt was right
[X fval exitflag output lambda grad hessian] = fmincon(@(x) fun(x,g_14,k_4) , x0, A, b, Aeq, beq,lb, up);
The problem is that your objective function returns a vector, while fmincon expects a scalar to minimize. Either you have some problem with your error definition or you want to get a least squares solution. If the second case, just do:
sw = ((log(1+x(1))*log(1+x(1)))+log(1+x(1)).*g_14 + k_4)/(1.6806) + ((log(1+x(2))*log(1+x(2))).*g_14 + ((log(1+x(3))*log(1+x(3))).*g_14 ;
sw = norm(sw);

  1 Comment

alejandro lopez
alejandro lopez on 19 May 2020
Hi Thiago, I'm very grateful for your answer.

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