Minimise a fitness function using GA toolbox having variable number of variables

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Rakesh Jain 2017-2-11

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评论： Walter Roberson 2017-2-11

I have an error function which I wish to minimise using GA. The error function can be a function of 1,2, 3 or many variables depending on the input given by the user. How should I write a fitness function for the GA toolbox? For example, if we have to minimise y which is a function of x, we create a separate matlab file with the command function y = abc(x) and use it in the GA toolbox. But in my case, the number of variables itself is not fixed. So how should I write such a fitness function ?

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Answer 1

Walter Roberson 2017-2-11

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https://ww2.mathworks.cn/matlabcentral/answers/324463-minimise-a-fitness-function-using-ga-toolbox-having-variable-number-of-variables#answer_254308

在 MATLAB Online 中打开

ga() always minimizes a function of one variable -- but the variable is permitted to be a vector.

For example,

F = @(x) (sum( (-x).^(0:length(x)-1) ) - 10000).^2
nvar = input('Number of variables?');
opts = optimoptions('ga', 'PlotFcn', @gaplotbestf, 'MaxGenerations', 1800);
[best_x, fval] = ga(F, nvar, [], [], [], [], [], [], [], opts)

(2 is the most interesting number of variables for the above)

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Rakesh Jain 2017-2-11

Getting following error on running the above code Error using optimoptions (line 114) Invalid solver specified. Provide a solver name or handle (such as 'fmincon' or @fminunc). Type DOC OPTIMOPTIONS for a list of solvers.

Error in abcd (line 3) opts = optimoptions('ga', 'PlotFcn', @gaplotbestf, 'MaxGenerations', 1800);

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