Calculate difference between two values per ID

[Anonymous]

Hello everyone I currently have this type of data set and was wondering if there is a way to calculate the difference month over month, with January being the first month, per employee. 

Employee ID	Amount	Date
1	100	1/1/2022
1	200	2/1/2022
1	300	3/1/2022
2	500	1/1/2022
2	600	2/1/2022
2	700	3/1/2022
3	150	1/1/2022
3	300	2/1/2022
3	450	3/1/2022

So that information would look something like this.

Employee ID	Amount	Difference	Date
1	100	0	1/1/2022
1	200	100	2/1/2022
1	300	100	3/1/2022
2	500	0	1/1/2022
2	600	100	2/1/2022
2	700	100	3/1/2022
3	150	0	1/1/2022
3	300	150	2/1/2022
3	450	150	3/1/2022

[Greg_Deckler]

@Anonymous Try:

Column = 
    VAR __Employee = [Employee ID]
    VAR __Date = [Date]
    VAR __Amount = [Amount]
    VAR __PrevDate = MAXX(FILTER(ALL('Table'),[Date]<__Date),[Date])
    VAR __PrevAmount = MAXX(FILTER(ALL('Table'),[Employee ID] = __Employee && [Date] = __PrevDate),[Amount])
    VAR __Result = __Amount - __PrevAmount
RETURN
    __PrevAmount

Basically MTBF pattern. See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/339586.
The basic pattern is:
Column = 
  VAR __Current = [Value]
  VAR __PreviousDate = MAXX(FILTER('Table','Table'[Date] < EARLIER('Table'[Date])),[Date])

  VAR __Previous = MAXX(FILTER('Table',[Date]=__PreviousDate),[Value])
RETURN
  __Current - __Previous

[Anonymous]

Hello @Greg_Deckler,

The formula has worked! I just had to switch the last part as that was just returning the previous amount as opposed to the result. I did have a question though. Is there a way to have it ignore the January value as it will have no comparison? Right now in the data it is showing the chart below, instead of a zero. Thanks for all the help!

Employee ID	Amount	Difference	Date
1	100	100	1/1/2022
1	200	100	2/1/2022
1	300	100	3/1/2022

[Greg_Deckler · Accepted solution]

@Anonymous Whoops, was troubleshooting. Yes, that can be done:

Column = 
    VAR __Employee = [Employee ID]
    VAR __Date = [Date]
    VAR __Amount = [Amount]
    VAR __PrevDate = MAXX(FILTER(ALL('Table'),[Date]<__Date),[Date])
    VAR __PrevAmount = MAXX(FILTER(ALL('Table'),[Employee ID] = __Employee && [Date] = __PrevDate),[Amount])
    VAR __Diff = __Amount - __PrevAmount
    VAR __Result = IF(__PrevAmount = BLANK(), BLANK(), __Diff)
RETURN
    __Result