Summing up till a certain interval

Question

How can I compute the summation of an interval. I will use Matlab\'s code for eg.

data=[1;2;3;4;5;6;7;8;9;10;11;12]

I would like to perform

Answer 1

No for loop needed, if indeed this interval is constant like in your example:

Ans=sum(reshape(data,3,[]))

note that I reshape the vector data to a matrix that has the right number of columns, so the value 3 relates to the interval size you wanted...