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

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!

Answer 1

[Alan Weiss]

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

[Ashley Thornton]

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

Answer 2

[Walter Roberson]

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()

Answer 3

[Leong Kit]

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)