Question

I have data in column A, and would like to put the averages in column B like this:

    a     b
1   10    10 
2   7     8.5
3   8     8.333
4   19    11
5   13    11.5

where b1 =average(a1), b2 =average(a1:a2), b3 =average(a1:a3)….

Using average() is alright for small amounts of data, but I have over 1500 data entries. I would like to find a more efficient way of doing this.

Answer 1

Make your initial range reference absolute, while the other is relative, i.e.:

b4 = average($a$1:a4)

You can paste that 1500 times an it will always increment the end of the range while keeping the beginning pinned to A1 due to the dollar signs in that reference.