Lets say I have two columns, A, B, and that the A column is in order from lowest to highest.
A | B
1 | 1.1
2 | 1.1
2 | 1.2
3 | 4.5
3 | 9.6
4 | 1.0
I am trying to sum up all of the values in column B that pertain to a specific value in column A. How can I do this the most efficiently? I know that the INDEX function can do this, but I do not want to manually find all of the different value groups, how large they are, and what rows they are at.