fmin additional variables ( are vector)

Question

alejandro lopez 2020-5-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/526055-fmin-additional-variables-are-vector

评论： alejandro lopez 2020-5-19

采纳的回答： Thiago Henrique Gomes Lobato

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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Answer 1

Thiago Henrique Gomes Lobato 2020-5-17

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/526055-fmin-additional-variables-are-vector#answer_432922

在 MATLAB Online 中打开

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);