MATLAB: How to collapse within a column vector

collapse in stata collapsing a column

Hello,
I am trying to collapse a long column to a shorter one by suming across elements. For instance, if I have:
x =
1
2
3
4
5
6
7
8
9
I would like to sum up every three elements and arrive at:
y= 6
15
24
This is basically the 'collapse' function in Stata but I'm struggling to do it in Matlab. Thanks for your advide.

Best Answer

You can use the sum function after reshape your vector into a matrix
vX = 1:9;
Interval = 3;
mX = reshape(vX, Interval, numel(vX)/Interval)
mX =
     1     4     7
     2     5     8
     3     6     9
sum(mX)
ans =
     6    15    24
/!\ reshape() won't work if the number of elements in vX is not a multiple of Interval
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