How can I convert symbolic equation to fitness function which can be evaluated by genetic algorithm

Question

Leong Kit 2014-1-21

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评论： Ashley Thornton 2015-8-20

Hi,

I have a symbolic equation and wish to convert to a function which can be evaluated by genetic algorithm (ga). I have tried using the matlabFunction and convert the symbolic equation into a matlab file. However, this generated file can only be evaluated by fmincon or patternsearch algorithms and not genetic algorithm. I get this error using ga.

Caused by: Failure in initial user-supplied fitness function evaluation. GA cannot continue.

It seems like the matlabFunction does not generate the format required by ga, can anyone please advise what's the solution/workaround to this problem?

Thanks!

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Answer 1

Alan Weiss 2014-1-22

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在 MATLAB Online 中打开

fmincon and patternsearch expect that the variable x is a column, though they are pretty forgiving if it is something else. ga expects that x is a row. So perhaps you should have

X = sym('x',[1 2*N]);

I could not check this because I do not know what P and price are.

Alan Weiss

MATLAB mathematical toolbox documentation

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Ashley Thornton 2015-8-20

Thanks so much. I was having the exact same problem, your solution worked a treat.

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Answer 2

Walter Roberson 2014-1-21

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Please show symvars() of the symbolic expression, and show the call to matlabFunction that you used. Please also show the first bit of the generated function -- in particular, the part inside the @() header. Please show your call to ga()

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Answer 3

Leong Kit 2014-1-21

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https://ww2.mathworks.cn/matlabcentral/answers/113163-how-can-i-convert-symbolic-equation-to-fitness-function-which-can-be-evaluated-by-genetic-algorithm#answer_121687

在 MATLAB Online 中打开

The code are as follow:

    N = 24;
    X = sym('x',[2*N 1]);
    Y = X(1:N);
    W = 3.2516e-6.*Y.^3 - 0.0010074.*Y.^2 + 0.390950.*Y+2.2353;
    Z = P.*W;
    totR = sum(Z);
    totR = subs(totR,[P],[price]);
    matlabFunction(totR,'vars',{X},'file','objFcn');
    % Call to ga
    x1 = ga(@objFcn, N*2, A, b, Aeq, beq)