# How to add values through a for loop?

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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

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 CommentsShowHide 1 older comment
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?

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 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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