Looking for MATLAB tip: running sum of a vector

[lethalfang]

Is there a faster way to do the following operation?
For a vector, I want a new vector such that, each element in the new vector is the sum of all the elements before it in the old vector.

I can do it with this loop:



old_vector = ones(1, 10); or
old_vector = [ 1 1 1 1 1 1 1 1 1 1]



for i = 1 : length(old_vector)
new_vector(i) = sum( old_vector( 1:i ) );
end



new_vector = 1 2 3 4 5 6 7 8 9 10



But I'm having a bunch of vectors whose lengths are on the order of 10^5, and this loop is really slowing things down. I wonder if there is a fast way to do it.

Thanks in advance!

[ahmatti]

That is called the cumulative sum and Matlab does have a function for it:


cumsum(old_vector)


That should speed things up considerably :)

[lethalfang]

That is called the cumulative sum and Matlab does have a function for it:


cumsum(old_vector)


That should speed things up considerably :)

Ohh yeah! Over 100x speed increase!!!