How to copy formulas with clustered data?

[Ezra]

Hi all,

I have a large dataset and I want to obtain the average of a group of
values grouped in 5 rows at the time, but when I copy it down, it skips
the data one row down, instead of five. For instance I use
=Average(A1:A5), and when I copy it down I want it to calculate
=Average(A6:A10), but instead it shows =Average(A2:A6). Does anybody
know how to do this?

My data looks like this (without the spaces between the lines):

Day Value
14 0.04
14 0.04
14 0.79
14 0.27
14 0.05

21 0.35
21 0.42
21 15.18
21 15.77
21 12.23

28 25.0
28 11.6
28 89.0
28 36.7
28 60.2

I need the average of the five values of day 14, 21, and 28

Thank you.
Gerardo

 

[Dave F]

Two possibilities:

1) SUMIF/COUNTIF

2) AVERAGE IF as an array formula.

To do 1, do: =SUMIF(A2:B16,14,B2:B16)/COUNTIF(A2:A16,14) where the criteria
is 14. Replace with the appropriate value.

I forget how to do 2, but I know it's possible.

Dave

 

[RagDyer]

Try this:

=AVERAGE(INDEX(A:A,5*ROWS($1:1)-4):INDEX(A:A,5*ROWS($1:1)))