Using SUMMARIZE to Count Values for a Range of Dates - dax

Question

I am trying to use SUMMARIZE to generate a table containing a list of people (represented by Phishing[Zid]) and the number of times where the person had a "Phishing Outcome" of "Fail" for a 12 month period. The 12 month period for each person will start on the date represented by Calendar[Month Index] and then I want to count the failures between that month index and month index - 11.
For example, assume the current row in the Phishing table has a Zid of wzqc51 and Calendar[Month Index] = 27. In the CALCULATE function I want to count the number of fails for month index between 16 and 27. It's the piece in angle brackets below that I cannot get right.
Also, there is a 1:M between Calendar and Phishing and the Calendar table is not a traditional daily calendar. It is a monthly calendar where month index of 1 is the first year and month of data and month index of say 27 is the 27th year and month of data we have.
SUMMARIZE(
Phishing,
Phishing[Zid],
Calendar[Month Index],
"Count", CALCULATE(
COUNT(Phishing[Zid]),
< I want to calculate a count between the current month index and month index - 11 >
Phishing2[Phishing Outcome]= "Fail"
)
)
The output should look like this:
Zid Month Index Count
QZ4TIN 27 4
This would mean that the user with a Zid of QZ4TIN failed four times between month index 16 and 27.

Answer 1

It's a bit tricky to write DAX without having data to test against, but I suspect you want something like
FILTER (
ALL ( Calendar ),
Calendar[Month Index] <= EARLIER ( Calendar[Month Index] ) &&
Calendar[Month Index] >= EARLIER ( Calendar[Month Index] ) - 11
)
Where EARLIER refers to the earlier row context (from the SUMMARIZE rather than the FILTER), not anything to do with dates or time.
You may wish to create a variable before the CALCULATE rather than using EARLIER
SUMMARIZE (
Phishing,
Phishing[Zid],
Calendar[Month Index],
"Count",
VAR CurrMonth = Calendar[Month Index]
RETURN
CALCULATE (
COUNT ( Phishing[Zid] ),
FILTER (
ALL ( Calendar ),
Calendar[Month Index] <= CurrMonth &&
Calendar[Month Index] >= CurrMonth - 11
),
Phishing2[Phishing Outcome] = "Fail"
)
)