Powerpivot 2016 measure using DAX to sum an array - arrays

Question

I want to sum the 7 preceding values of a row as a measure like so:
| Wk_number | Value A | Measure | Array |
-------------------------------------------
| 01 | 1 | N/A# | N/A# |
| 02 | 1 | 1 | {01} |
| 03 | 10 | 2 | {01-02} |
| 04 | 3 | 12 | {01-03} |
| 05 | 5 | 15 | {01-04} |
| 06 | 10 | 20 | {01-05} |
| 07 | 1 | 30 | {01-06} |
| 08 | 4 | 31 | {01-07} |
| 09 | -10 | 34 | {02-08} |
| 10 | 3 | 26 | {03-09} |
| 11 | 2 | 18 | {04-10} |
etc...
I added the array column just to clarify the example how of the sum is comprised, notice that from wk09 it's not simply a running total.
How to do this using DAX statements?

Answer 1

Two ways to do this: you can either create a calculated column, or a measure.
For the column:
=CALCULATE(SUM([Value A]),FILTER(Table,Table[Wk_number]<EARLIER(Table[Wk_number]) && Table[Wk_number] >= (EARLIER(Table[Wk_number])-7)))
For the measure, it's a very similar formula but instead of using EARLIER(), we use MAX():
=CALCULATE(SUM([Value A]),FILTER(ALL(Table3),Table3[Wk_number]<MAX(Table3[Wk_number]) && Table3[Wk_number] >= (MAX(Table3[Wk_number])-7)))
Below is a screenshot of the results. A few of the numbers in your example table seem to be off based on the math: