MATLAB: Ga-fitness

ga

Dear All,
I need to optimize parameters of a function using the ga module. I have a coefficient matrix say A(9:4):
A =
   -0.0996   -0.0323   -0.0640   -0.0365
    0.0859   -0.0636    0.0552    0.0315
    0.1805    0.0125    0.1159    0.0662
    0.0521    0.0513    0.0335    0.0191
   -0.3028    0.0647   -0.1946   -0.1111
   -0.2242   -0.0382   -0.1440   -0.0822
    0.0475   -0.0191    0.0305    0.0174
    0.2170   -0.0010    0.1394    0.0796
    0.0437    0.0257    0.0281    0.0160
and a vector B where i store the experimental data say B(9:1):
B =
   -4.8700
   -3.2100
    5.1000
    5.3400
   -1.6200
   -8.1700
   -0.4700
    4.8300
    3.0800
my chromosome will be a vector x(4:1)
I use this fitness function:
FitnessFcn = @(x)bsxfun(@minus,abs(bsxfun(@times,A,x)),B)
But when I am using
[x]=ga(FitnessFcn,4)
I get:
??? Subscripted assignment dimension mismatch.
Error in ==> fcnvectorizer at 14
            y(i,:) = feval(fun,(pop(i,:)));
Error in ==> makeState at 47
        Score = fcnvectorizer(state.Population(initScoreProvided+1:end,:),FitnessFcn,1,options.SerialUserFcn);
Error in ==> gaunc at 41
state = makeState(GenomeLength,FitnessFcn,Iterate,output.problemtype,options);
Error in ==> ga at 279
        [x,fval,exitFlag,output,population,scores] = gaunc(FitnessFcn,nvars, ...
Caused by:
    Failure in user-supplied fitness function evaluation. GA cannot continue.
Could you please help me resolve the problem.
Thanks

Best Answer

http://www.mathworks.com/help/toolbox/gads/ga.html
The objective function, fitnessfcn, accepts a vector x of size 1-by-nvars, and returns a scalar evaluated at x.
However your expression abs(bsxfun(@times,A,x)) is going to result in 9 x 4, and when you @minus the 9 x 1 B from that you are going to get 9 x 4. And that isn't a scalar.
Related Question