MATLAB: Cumulative sum of an array

MATLAB

Hi, so I have an array,b, I need to find the cumulative sums for every 5 values.
To calculate the cumulative sum S of an array a with 5 values
 b=[1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0];
a=[1 2 3 4 5];
amean=mean2(a);
S=zeros([1 length(a)]);
S(1)=a(1)-amean
for i=2:5
  S(i)=S(i-1)+(a(i)-amean)
end
S=-2    -3    -3    -2     0
The result for b should look like S = -2 -3 -3 -2 0 0 1 3 6 0 -2 -3 -3 -2 0 0 1 3 6 0

Best Answer

   br=reshape(b,5,[]);
   S=reshape(  cumsum(br-mean(br))   ,1,[])
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