MATLAB: Plot the function value according to the value of the optimized parameter by genetic algorithm

ga

Dears,
I would like to extract the value of the optimized parameters x* and the value of the function at each step of the optimization.
From my initial search on the internet there is a way using the plot functionality, but I was not able to get the funtion value Y in terms of the optmized parameters values X* at each step neither
The optimization methodology is GA.
Could you please help me with that.

Best Answer

This example shows how to extract the best objective function value and the corresponding x vector at each iteration
global x_iterations y_iterations
x_iterations = [];
y_iterations = [];
obj_fun = @(x) sum(x.^2);
opts = optimoptions('ga', 'OutputFcn', @myOutFcn);
[x_final, f_final] = ga(obj_fun, 10, [], [], [], [], [], [], [], opts);
function [state, options, optchanged] = myOutFcn(options, state, ~)
    global x_iterations y_iterations
    [best_val, idx] = min(state.Score);
    best_x = state.Population(idx,:);
    x_iterations = [x_iterations; best_x];
    y_iterations = [y_iterations; best_val];
    optchanged = false;
end
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