MATLAB: Which method to use, basic for loop or loop through values of a vector

efficientfor loop

Vector ind has indices I want to loop through, x has values.
ind = [1     3     5];
x = [10    20    30    40    50    60    70];
ind_len = size(ind,2)
Approach 1: When using a for loop, should I use the basic incremental for loop, where I access each element of x with index values from ind vector 
for i = 1:ind_len
x(ind(i))
end
Approach 2: Don't use ind_len length variable and assign ind vector to for loop
for i = ind
x(i)
end
Which method is efficient ?

Best Answer

x = rand(1, 1e6);
y = zeros(size(x));
ind = randperm(numel(x));
tic
for loop = 1:10
  for k = 1:numel(ind)
      y(ind(k)) = x(ind(k));
  end
end
toc
tic
for loop = 1:10
  for k = ind
      y(k) = x(k);
  end
end
toc
% Elapsed time is 0.395765 seconds.
% Elapsed time is 0.739708 seconds.
The first approach can be handled more efficiently.
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