Create a Column using DAX that flags if a row existed in the previous month based on a ID Field

Question

Hi All&nbsp;I want to create a Column that flags if a record existed in the previous month, so that if it didn't I can exclude it from the current months calculations.&nbsp;ID&nbsp; &nbsp; &nbsp;Month

1&nbsp; &nbsp; &nbsp; &nbsp;Jun-19

2&nbsp; &nbsp; &nbsp; &nbsp;Jun-19

3&nbsp; &nbsp; &nbsp; &nbsp;Jun-19

4&nbsp; &nbsp; &nbsp; &nbsp;Jun-19

1&nbsp; &nbsp; &nbsp; &nbsp;May-19

2&nbsp; &nbsp; &nbsp; &nbsp;May-19

3&nbsp; &nbsp; &nbsp; May-19So in the example above, I want 3rd Column that tells me for example that ID 4 did not exist in MayI want to do this for every record&nbsp;Any guidance appreciated!&nbsp;

anonymous · Answer

What is the data type of the Month column?&nbsp;BestDarek

anonymous · Answer

Date/Time

anonymous · Answer

[Existed In Prev Month] = -- calculated column
-- T[Month] must be the first day of the month
var __currentMonth = T[Month]
var __currentID = T[ID]
-- This moves the MONTH to be the first day
-- of the prior month.
var __prevMonth = EDATE ( __currentMonth, -1 )
var __existedInPrevMonth =
	not isempty(
		filter(
			T,
			T[ID] = __currentID,
			T[Month] = __prevMonth 
		)
	)
return
	__existedInPrevMonthBestDarek

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Create a Column using DAX that flags if a row existed in the previous month based on a ID Field

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