This error is generated when a matrix is initially defined with certain dimensions and later in the program data is fed to the matrix (typically using for-loops) which exceeds the defined dimensions. Either the dimensions can be increased or the data reduced.

You have to check weather your matrices are compatible for multiplication, addition or subtraction??? If yes it will work, otherwise you will be getting such problem.

I would like to suggest you to download this best book "http://www.cse.zju.edu.cn/eclass/attachments/2015-10/01-1446085870-145420.pdf" for your future back up studies.

I assume your input, X, is a 3x10 double. Then you need to set P, C and Q to take the full row, rather than a single number. And say which element of Zi you are setting in the loop. It is also good practice to declare your Zi variable before you change it's size on each loop. Like below:

function [ Zi ] = myfitness( X )

P=X(1,:);

C=X(2,:);

Q=X(3,:);

% Zi= fitness value

% C,P,Q = variables vectors

Zi=zeros(10,1);

for i=1:10

Zi(i) = P(i).*Q(i)-C(i).*Q(i);

end

end

Dear Sir Thomas Welton , yes my imputs are 4*10 double .. please check what i get after i modified the function as you suggest

@ Ranjan Parekh

عائشة غدامسي , you need to call myfitness with X as the input.

X=rand(3,10)

myfitness(X)

Muhammad Ali when i run the function it works normally but in the ga toolbox it doesn't

thanks a lot for the book , may allah bless you

Thomas Welton errors in main function

& when i renamed myfitness to myfitness(X) i got: myfitness(x) is not formed from a valid MATLAB identifier

You don't need to rename the file i.e. "myfitness(X).m".

May you follow Thomas Welton's suggestions as above. It works.