Array indices must be positive integers or logical values. Error in WCA (line 44) pop(i).cos​t=objectiv​e_function​(pop(i).po​sition); I am getting this issue while I am running the code of distribution load flow analysis

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AR Hithesh
AR Hithesh 2021-4-16
回答： Walter Roberson 2021-5-3
I have attached two files in this questions, the objective is to call the fx file in BackawardFarwardNew_28bus.m to implement the WCA !!, could you please tell how to integrate or what is the issue i am facing here, its quite urgent..!!
for i=1:Npop
pop(i).position=LB+(UB-LB).*rand(1,nvars);
pop(i).cost=objective_function(pop(i).position);
this is the 44th line of water cycle algorithm where i got the error

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回答（1 个）

Walter Roberson
Walter Roberson 2021-5-3
In BackwardFarwardNew_28bus.m you have
objective_function = min(P_l);
[Xmin,Fmin,NFEs,Elapsed_Time]=WCA(objective_function,LB,UB,nvars,Npop,Nsr,dmax,max_it)
so you are taking min() of something and passingå it in as objective_function .
What is that thing, P_l ? Well, you have
for i=size(LD,1):-1:1
c=[];
P_l = [];
e=[];
[c e]=find(LD(:,2:3)==LD(i,3));
if size(c,1)-1==0
IB(LD(i,1))=I(LD(i,3));
x = LD(:,4);
P_l = real(((IB(LD(i,1)))^2).*x)
else
IB(LD(i,1))=I(LD(i,3))+sum(IB(LD(c,1)))-IB(LD(i,1));
x =LD(:,4);
P_l = real(((IB(LD(i,1)))^2).*x)
end
end
That runs a loop (backwards), and every iteration of the loop it resets all of P_l to empty, and then it sets P_l to P_l = real(((IB(LD(i,1)))^2).*x) where x = LD(:,4); looks like a column vector. So P_l appears that it will be a column vector after the for loop. With the .* operator, it is most likely numeric, but at the moment we cannot rule out symbolic or even something more strange such as transfer function.
So what is IB ?
IB=zeros(size(LD,1),1);
That is numeric, as was most likely.
So, you loop backwards over the rows of LD, and each time you overwrite all of P_l with a numeric vector. Then afterwards you take min() of the numeric vector, giving a numeric scalar result. And you pass that numeric scalar result into WCA.
What does WCA do with it?
% Water Cycle Algorithm (WCA) (Standard Version)
% This code is prepared for single objective function (minimization), unconstrained, and continuous problems.
so WCA is expecting to minimize a function. Most likely the first parameter,
function [Xmin,Fmin,NFEs,Elapsed_Time]=WCA(objective_function,LB,UB,nvars,Npop,Nsr,dmax,max_it)
objective_function. But you passed a numeric scalar into that position.
pop(i).cost=objective_function(pop(i).position);
objective_function is a numeric scalar. The only valid indices for it are scalar true, any number of false, and any number of numeric 1 . But
pop(i).position=LB+(UB-LB).*rand(1,nvars);
That is not going to be true, false, or 1.
You need to review your BackwardFarwardNew_28bus.m and figure out what it is that you want to minimize. You need to be passing in a function handle, and the function handle has to expect to receive (in the context of your code) a vector of length 6, and the function handle has to return a scalar numeric value.

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