# I try to write simple analytical function Gomez and Levy with ga in optimization toolbox but it cannot run

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sogol bandekian on 7 May 2022
Commented: Walter Roberson on 24 May 2022
%fitness function Gomez and Levy
function y=fitnessfunctiongl(x)
x1=x(1);
x2=x(2);
y=(4*x1.^2)-2.1*x1.^4+1/3*x1.^6+(x1*x2)-4*x2.^2+4*x2.^4;
end
¬¬¬¬¬%constraints
function [c ,ceq]=constraintgl(x)
x1=x(1);
x2=x(2);
c=-sin(4*pi*x1)+2*sin(2*pi*x2)^2-1.5;
ceq=[];
end
%main script to pass function and constraints to ga for optimization
ObjFcn=@fitnessfunctiongl;
nvars=2;
lb=[-1, -1];
ub=[0.75, 1];
nonlcon=@constraintgl;
options = optimoptions('ga','ConstraintTolerance',1e-6,'Display','iter','PlotFcn',{@gaplotrange,@gaplotbestf,@gaplotselection,@gaplotmaxconstr}); %plotting the process of finding the solution
%solution and function value
[x , fval,exitFlag,output,population,scores]= ga(ObjFcn,nvars,[],[],[],[],lb,ub,nonlcon,options);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%errors
[state,optimvalues] = callOnePlotFcn(fname,plotNames{i},state,options.OutputPlotFcnOptions,optimvalues,'init',args{i}{:});
Error in gacon (line 55)
Error in ga (line 406)
[x,fval,exitFlag,output,population,scores] = gacon(FitnessFcn,nvars, ...
Error in maingl (line 11)
[x , fval,exitFlag,output,population,scores]= ga(ObjFcn,nvars,[],[],[],[],lb,ub,nonlcon,options);
##### 2 CommentsShowHide 1 older comment
sogol bandekian on 10 May 2022
Error using makeState (line 61)
Your fitness function must return a scalar value.
Error in gacon (line 44)
state = makeState(GenomeLength,SubFitness,Iterate,subtype,options);
Error in ga (line 406)
[x,fval,exitFlag,output,population,scores] = gacon(FitnessFcn,nvars, ...
Error in maingl (line 11)
[x , fval,exitFlag,output,population,scores]= ga(ObjFcn,nvars,[],[],[],[],lb,ub,nonlcon,options);

Walter Roberson on 10 May 2022
y=(4*x1.^2)-2.1*x1.^4+1/3*x1.^6+(x1*x2)-4*x.^2+4*x2.^4;
Notice that you have 4*x.^2 . But x is a vector so that would return a vector.
Walter Roberson on 24 May 2022
The plots are not empty. The optimization is configured for a maximum number of generations and that is the x axis used so that it does not get continually redrawn as more generations are processed. The optimization either succeeded or failed in a small number of generations, on the order of 5 generations.

Bhavana Ravirala on 10 May 2022
Hi Sogol,
When I try to reproduce the issue at my end I encountered the error as Function definition not supported in this context. Create functions in a code file. If you are facing the same error refer to the below link to eliminate the error.
If not, can you send us the exact error message that you are getting.
Hope this helps!!
sogol bandekian on 10 May 2022
hello thank you for reply.these below errors are what I got
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Error using makeState (line 61)
Your fitness function must return a scalar value.
Error in gacon (line 44)
state = makeState(GenomeLength,SubFitness,Iterate,subtype,options);
Error in ga (line 406)
[x,fval,exitFlag,output,population,scores] = gacon(FitnessFcn,nvars, ...
Error in maingl (line 11)
[x , fval,exitFlag,output,population,scores]= ga(ObjFcn,nvars,[],[],[],[],lb,ub,nonlcon,options);