How can i create a multivariable function from matrix data?

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Natanael Acencio Rijo 2013-12-4

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评论： sixwwwwww 2013-12-4

Hi i´m new to matlab. Im trying to create a program that reads data out of a matrix and assigns those values to variables. the issue is that this must be a function for which im going to evaluate its minima, so i cannot define p.

My problem is of this kind:

im going to evaluate the minimum value possible of p

A=[150;

   200;
   300;]

I want to generate this from the previous data:

f(1)=A(1,1)*p(1)

f(2)=A(2,1)*p(2)

f(3)=A(3,1)*p(3)

resulting at the end that

Totalcost= f(1)+f(2)+f(3); which will a multivariable function.

I tried to use a for loop in this case but it doesnt let me assign the values in the parenthesis to the p, to make it a different variable. it keeps telling me that i´m reffering to a value that has been cleared.

what i want to know is: which commands can i use to assign values to the p as a variable of a multivariable function?

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Natanael Acencio Rijo 2013-12-4

编辑：Natanael Acencio Rijo 2013-12-4

I finally got the result for the function to minimize, but it´s still in sym class, so it doesnt let me evaluate it for optimization. but it doesnt let me convert the variables p to double class, so that the optimization algorithm can input values in it.

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采纳的回答

sixwwwwww 2013-12-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/108560-how-can-i-create-a-multivariable-function-from-matrix-data#answer_117207

编辑：sixwwwwww 2013-12-4

在 MATLAB Online 中打开

if you have symbolic toolbox installed then you can do it as follows:

A = [150; 200; 300]; 
p = sym('p%d', [1 numel(A)]);
for i = 1:numel(A)
    f(i) = A(i) * p(i);
end
Totalcost = sum(f(:));
disp(Totalcost)

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Natanael Acencio Rijo 2013-12-4

ans =

5.3*p(1) + 5.5*p(2) + 5.8*p(3) + 0.004*p(1)^2 + 0.006*p(2)^2 + 0.009*p(3)^2 + 1100.0

this is my final result, what i want to do then is being able to find its minimum, but it is in sym class and the optimization toolbox doesnt accept the variables.

sixwwwwww 2013-12-4

you need to subsitutute values for symbols p(1), p(2), ... then you can get numeric values in symbols which you can convert to double type using doouble()

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