How to subtract Row Values (previous Row Value) grouped by Name

[apvu2]

I was wondering if there was a way to subtract a previous row value grouped by lets say Name. The screenshot of what I am trying to achieve is below. If there was no previous row for the individual there wouldnt be a value to subtract. I also sorted name and year by ascending order. In power query or Dax it does not matter, I just need that difference column. 

(Same Table Copy and pasted) 

Name	Year	Difference
A	2019	N/A
A	2020	1
A	2021	1
B	2020	N/A
B	2021	1
C	2019	N/A
C	2022	3
C	2023	1

[Greg_Deckler · Accepted solution]

@apvu2 Try:

Difference Column = 
  VAR __Name = [Name]
  VAR __Year = [Year]
  VAR __Previous = MAXX(FILTER('Table',[Name] = __Name && [Year] < __Year),[Year])
RETURN
  __Year - __Previous

[Anonymous]

Hi @Greg_Deckler ,

I'm trying to use your formula here, but it seems like the formula can't detect my column name, as it only detect for "measure". May i know why and how do i fix this ?

[apvu2]

Hey Greg, 

Thank you so much this would definitely work!!!!!!!!!!!!!!!!!