how to dynamically retrieve previous months data

[semidevil]

I have my data set more or less structured in the following where I have these columns:

A datetime column (date format)

a yearMonth(i,e YYYYMM) column (number format)

value column (number format).

I need to create a bar graph where with 3 bars:

a 2016 bar that sums up the value at 201612 (never change)

a 2017 bar that sums up the value at 201712 (never change)

a 2018 bar that will always sum the previous months values  So in February 2018, it will sum up the value of Jan 2018

right now, I created an additional column that has a "TRUE" indicator if YYYYMM = (201612 or 201712), and I can use that as a filter....but I dont know how to make the 2018 bar "dynamic". 

I thought about creating yet another "PreviousMonth" column that looks outputs the current YearMonth as a number format, roll that back one month, and if (YYYMM = "PreviousMonth", TRUE, FALSE), but I dont know how to make that work.

How would I go about doing this?

[Greg_Deckler · Accepted solution]

Why not a measure like:

2018 = CALCULATE(SUM(Table[Value]),FILTER(Table,[yearMonth] > 201800 && [yearMonth] < MAX(Table[yearMonth)-1))

Something like that.