How to add values through a for loop?

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Hail
Hail on 13 Aug 2014
Commented: Salman Tahir on 14 Sep 2017
I have a for loop that creates something like this:
first iteration: [1 2 3 4 5 6 7] second iteration: [2 3 4 5 6 7 8] third iteration: [3 4 5 6 7 8 9]
(these aren't my actual values, just an example)
I want my loop to add all of these together at the end. So I would get an output of:
[6 9 12 15 18 21 24]
How can I do this?
Thanks

Accepted Answer

Adam
Adam on 13 Aug 2014
Edited: Adam on 13 Aug 2014
Just pre-size a vector before the for loop as e.g.
result = zeros( 1, 7 );
then inside the for loop:
result = result + newValues;
where newValues are the results calculated in that iteration. Unfortunately Matlab doesn't have a += operator.
That will add them together as you go. If you really want to only do so at the end then you'd have to store an ( n * m ) matrix for n iterations with length m result and then sum along the relevant dimension.
  2 Comments
Salman  Tahir
Salman Tahir on 14 Sep 2017
what do you mean by " If you really want to only do so at the end then you'd have to store an ( n * m ) matrix for n iterations with length m result and then sum along the relevant dimension."? what is this process called? Is there a place I can look this up?

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More Answers (2)

Joseph Cheng
Joseph Cheng on 13 Aug 2014
there are two methods. if you need to save each iteration then in the for loop save it like below:
for iter = 1:3
%calculations here to get your values A.
A(iter,:) = randi(10,1,7); % my dummy iteration values
end
SumA = sum(A);
if you don't need to save each iteration.
SumA = 0;
for iter = 1:3
%calculations here to get your values A.
SumA = SumA + randi(10,1,7); % my dummy iteration values
end

Salman  Tahir
Salman Tahir on 14 Sep 2017
what do you mean by " If you really want to only do so at the end then you'd have to store an ( n * m ) matrix for n iterations with length m result and then sum along the relevant dimension."? what is this process called? Is there a place I can look this up?

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