Calculate the difference between quantities per month over two years

[Dan_B]

I am trying to do a simple calculation that is not being very easy to do.   I am trying to find the difference in quantity for each month in 2019 and 2020.    I split out the creation date into Month and Year so I can total them and then find the difference.  My visualization has three columns and I am trying to calculate the forth (see below).  ALL the data is in one Table.  My row is Month, column is Year and value I am summing is Drop Quantity.  I tried different commands but I guess I just don't know DAX good enough yet. 

Month	2019	2020	Diff
1	555	444
2	666	222
3	777	555
4	888	444
5	999	333
6	111	50
7	222
8	333
9	444
10	555
11	666
12	777

[Dan_B]

Thank you, that worked!  I read so many different ways of doing it I confused myself.  I think your solution was the easiest way to go.  Thanks again.   

[lbendlin · Accepted solution]

Not proud of this one but here goes:

Create two measures

2019 =

var m = SELECTEDVALUE('Values'[Month])

return calculate(sum('Values'[Value]),'Values'[Year]=2019,'Values'[Month]=m)

2020 =

var m = SELECTEDVALUE('Values'[Month])

return calculate(sum('Values'[Value]),'Values'[Year]=2020,'Values'[Month]=m)

Then create a matrix visual with the Month as rows. NOTHING as columns, and the two measures as values.

Lastly create another measure

diff = [2020]-[2019]

and also add to the values area.

May need cleanup for the scenario where 2020 values are blank - not sure what you want to do in such a case.