# Why this piece of code gives error?

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Sadiq Akbar on 16 Oct 2022
Commented: Sadiq Akbar on 16 Oct 2022
The following piece of code gives error:
Positions=rand(30,3);
fobj=@fun4sn0;
for i=1:size(Positions,1)
Fit(i) = fobj(Positions(i,:));
end
The error it gives is as:
Array indices must be positive integers or logical values.
Error in fun4sn0 (line 18)
xo(1,k)=xo(1,k)+u(i)*exp(-1i*(k-1)*pi*cosd(u(P+i)));
Error in abc (line 4)
Fit(i) = fobj(Positions(i,:));
KSSV on 16 Oct 2022

Walter Roberson on 16 Oct 2022
Positions=rand(30,3);
Three columns
Fit(i) = fobj(Positions(i,:));
You pass in one row at a time, so you pass in a vector with one row and three columns.
function e=fun4sn0(pop)
where it is received as pop
C = size(pop,2);
P=C/2;
3 columns so C is 3 and P is 1.5
for i=1:P
i is 1:1.5 which will be just 1
xo(1,k)=xo(1,k)+u(i)*exp(-1i*(k-1)*pi*cos(u(P+i)));
P is 1.5 so P+i will be 2.5 and you will be indexing u at 2.5 which is not a valid index
u=[25 45 ];% desired vector
You hard-coded u to be length 2 but you can see that you are indexing u according to the size of the input vector, which will be a problem if the input gets larger.
Sadiq Akbar on 16 Oct 2022
Thanks a lot for your help.