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

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Ankur Shah on 20 Aug 2021
Commented: Debaditya Gupta on 31 Mar 2022
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.
Debaditya Gupta on 31 Mar 2022
How to get similar type of graph in Particle Swarm Optimization in matlab?
Matlab PSO script is showing only iteration vs best fitnes value, but mean fitness value is not showing

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 CommentsShowHide 1 older comment
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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