Not enough input arguments

Hi, I'm trying to turning a genetic algorithm for the following function :

function L=fonction(x1,x2,x3)

L=abs(118.04-(x1.*218.46+x2.*31.09+x3.*125.61));

end

but when i wrote the following command :

 [x1,x2,x3,Fval,exitFlag,Output] = ga(@fonction,3);

fprintf('The number of generations was : %d\n', Output.generations);

fprintf('The number of function evaluations was : %d\n', Output.funccount);

fprintf('The best function value found was : %g\n', Fval);

matlab return this error :

Error using fonction (line 2)

Not enough input arguments.

Error in createAnonymousFcn>@(x)fcn(x,FcnArgs{:}) (line 11)

fcn_handle = @(x) fcn(x,FcnArgs{:});

Error in fcnvectorizer (line 14)

              y(i,:) = feval(fun,(pop(i,:)));

Error in makeState (line 47)

          Score = fcnvectorizer(state.Population(initScoreProvided+1:end,:),FitnessFcn,1,options.SerialUserFcn);

Error in gaunc (line 41)

state = makeState(GenomeLength,FitnessFcn,Iterate,output.problemtype,options);

Error in ga (line 351)

              [x,fval,exitFlag,output,population,scores] = gaunc(FitnessFcn,nvars, ...

Caused by:

      Failure in user-supplied fitness function evaluation. GA cannot continue.

Please help

Answer 1

[Geoff Hayes]

nesrine - the problem is how you have defined the signature for your fitness function, fonction. Check out the documentation from MATLAB Genetic Algorithm as it relates to the function handle that you pass to ga

fitnessfcn: Handle to the fitness function. The fitness function should accept a row vector of length nvars and return a scalar value.

As described above, the fitness function accepts one input row vector of length nvars. In your case, that would be a row vector of size three. The above code has defined your fitness function to accept three inputs and NOT one. The error message Not enough input arguments is caused because the GA is passing only one input (a row vector with three elements) to your function that requires three inputs.

You just need to change your code to accept a single row vector instead of three variable inputs

 function L=fonction(xData)

     x1 = xData(1);
     x2 = xData(2);
     x3 = xData(3);

     L=abs(118.04-(x1*218.46+x2*31.09+x3*125.61));

 end

Try the above and see what happens!

[Ulyana Dudko]

Thank you, Geoff! Very helpful!