Why this piece of code gives error?

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Sadiq Akbar el 20 de Abr. de 2022
Comentada: Steven Lord el 21 de Abr. de 2022
CostFunction='fun4sn0';
nPop=120;
nVar=4;%nVar=1000;
nPop_Initial=nPop;
nPop_Final=30;
MaxNFE=3e3;
MaxIter0=ceil(MaxNFE/((nPop_Initial+nPop_Final)/2)); % Approximate Maximum Iterations
Cr=0.5;
xmin=[0 0 0 0];
xmax=[10 10 pi pi];
%%%%%%%%%%%
NFE=0;
Gbest.Position=[];
Gbest.Cost=inf;
BestCosts=nan(1,MaxIter0);
nfe=BestCosts;
for i=1:nPop
Velocity(i,:)=zeros(1,nVar); %#ok<*SAGROW>
Position(i,:)=xmin+(xmax-xmin).*rand(1,nVar);
Cost(i)=CostFunction(Position(i,:));
PbestPosition(i,:)=Position(i,:);
PbestCost(i)=Cost(i);
PbestVel(i,:)=Velocity(i,:);
if PbestCost(i)<Gbest.Cost
Gbest.Position=PbestPosition(i,:);
Gbest.Cost=PbestCost(i);
Gbest.Velocity= PbestVel(i,:);
end
end
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Jon el 20 de Abr. de 2022
what error does it give, please cut and paste entire error message
Sadiq Akbar el 20 de Abr. de 2022
Thank you very much dear Jon for your response. It gives the following error:
Subscript indices must either be real positive integers or logicals.
Error in WGA1 (line 37)
Cost(i)=CostFunction(Position(i,:));

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Steven Lord el 20 de Abr. de 2022
Either make your CostFunction variable a function handle to the fun4sn0 function (which is the approach I'd prefer):
CostFunction= @fun4sn0;
or use feval to evaluate the function by name.
Cost(i) = feval(CostFunction, Position(i, :));
Both of these assume that your function returns a scalar, since you're assigning its output into one element of the Cost variable.
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Image Analyst el 21 de Abr. de 2022
@Steven Lord messing with function handles and feval() seems like a roundabout way to do it. Is that better than just calling the function directly like I suggested?
Cost(i) = fun4sn0(Position(i,:));
Steven Lord el 21 de Abr. de 2022
@Image Analyst That is another option, and is the easiest if you want to hard-code the cost function. I think that particular name put me in "this is likely going to be used in some form of optimization" mode and in that case (the "function function" scenario, see ode45, fminsearch, fzero, integral, etc.) to keep the code as a general purpose solver you wouldn't want to hard-code the function.

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Más respuestas (1)

Image Analyst el 20 de Abr. de 2022
CostFunction is a character array, not an actual function. Did you mean
Cost(i) = fun4sn0(Position(i,:));
Cost(i)=CostFunction(Position(i,:));
Thorough discussion of the error in the FAQ:
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Sadiq Akbar el 21 de Abr. de 2022
Also thanks a lot dear Image Analyst.

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