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Find values for best and mean fitness value for each generation in Genetic Algorithm

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Ankur Shah
Ankur Shah on 20 Aug 2021
Commented: Alan Weiss on 25 Aug 2021
After running GA, using Optimization toolbox and code below, the following mean and best fitness value graph was obtained.
[x,fval,exitflag,output,population,score] = ...
ga(@revisepartialmodespring,nvars,[],[],[],[],lb,ub,[],[],options);
How to get the value of best fitness at each generation ?.. I wanted to show a comparison of the best fitness v/s generation for different problems on the same graph. Hence I need values to best fitness at each generation.

Accepted Answer

Alan Weiss
Alan Weiss on 22 Aug 2021
Use a Custom Output Function for Genetic Algorithm. Model it on the gaplotbestf plot function. To see that function,
edit gaplotbestf
Alan Weiss
MATLAB mathematical toolbox documentation
  2 Comments
Alan Weiss
Alan Weiss on 25 Aug 2021
options = optimoptions("ga","OutputFcn",@gascoreoutfun);
rng default % For reproducibility
x = ga(@ps_example,2,[],[],[],[],[],[],[],[],options)
Optimization terminated: average change in the fitness value less than options.FunctionTolerance.
x = 1×2
-4.6793 -0.0860
size(gapopulationhistory)
ans = 1×2
122 2
function [state,options,optchanged] = gascoreoutfun(options,state,flag)
persistent history
optchanged = false;
switch flag
case 'init'
history = [min(state.Score),mean(state.Score)];
assignin('base','gapopulationhistory',history);
case 'iter'
history = [history;min(state.Score),mean(state.Score)];
assignin('base','gapopulationhistory',history);
case 'done'
end
end
Alan Weiss
MATLAB mathematical toolbox documentation

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