Saving / Showing Value of Variables in Genetic Algorithms

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Marc Erhard
Marc Erhard 2015-2-24
回答： Gifari Zulkarnaen 2020-4-6
Hi there, I want to solve a problem using matlab.
It´s working great, I´m getting a solution after XXX generations.
But, it is only displaying me the FINAL solution for x(1) and x(2), the coordinates of the optimum solution. Let´s just say, I want to display the values of x(1) and x(2) after every iteration.
I want to show / save ALL values of x(1) and x(2) in the fitness function, so I can plot it in excel and show like: Generation 1 x(1) and x(2) was bad solution Generation 2 better etc etc Generation XXX x(1) and x(2) are optimal
Any idea? its driving me crazy, tried the iterative display, this is getting me nowhere.
Please be patient, I am a beginner with matlab...
Best regards, Marc

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回答（4 个）

Alan Weiss
Alan Weiss 2015-5-26
Use an output function to get whatever you like from each iteration. There are examples using output functions in a different syntax here (careful, fmincon and ga use different syntax for their output functions, but the idea is the same).
Alan Weiss
MATLAB mathematical toolbox documentation
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Precious Ogbeiwi
Precious Ogbeiwi 2019-3-20
Hi Alan,
Do you have an example for this function for genetic algorithm? I have been trying to convert the fmincon syntax to ga syntax but it has not run. Your help would be truly appreciated.
Many thanks.
Precious Ogbeiwi

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Geoff Hayes
Geoff Hayes 2015-2-25
Marc - according to Genetic Algorithm, all you need to do is include the output variable as an output parameter of the ga function. Something like
[x,fval,exitflag,output] = ga(fitnessfcn,nvars,...)
and output will be a structure that contains output from each generation and other information about the performance of the algorithm. Does this not include the optimal solution found at each generation?
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Geoff Hayes
Geoff Hayes 2015-2-26
Marc's answer moved here
hey Geoff!
Thanks again for your answer, i reall appreciate it!
Still it does not work...
>> [x,fval,exitflag,output] = ga(@simplefitness,2) Optimization terminated: average change in the fitness value less than options.TolFun.
x =
44.8535 64.2461
fval =
3.7211e+04
exitflag =
1
output =
problemtype: 'unconstrained'
rngstate: [1x1 struct]
generations: 86
funccount: 4350
message: 'Optimization terminated: average change in the fitness value less than options.Tol...'
maxconstraint: []
Geoff Hayes
Geoff Hayes 2015-2-27
Marc - the output structure is disappointing. I would have thought that it would include some basic statistics on each generation.
You may have to look at using an output function that fires at each generation. See ga options output functions for details. Based on the documentation, your output function would have the following signature
[state,options,optchanged] = myfun(options,state,flag)
where the input state structure has these properties which includes population and score which you could perhaps use to determine which member of the current population has the bet fitness. You could then write this data to file (or a persistent variable) for future analysis.

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Sri
Sri 2015-5-26
Marc did you find the solution? I have a similar problem. I want the values of x(1) and x(2) after optimization
Gifari Zulkarnaen
This guy here give an example output function to obtain variable in each iteration on a pattern search optimization. Maybe it is similar with genetic algorithm.
https://www.mathworks.com/matlabcentral/answers/514018-passing-variable-through-pattern-search-iterations

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