Help: Inverse Cumulative

[Anonymous]

Hello Everyone,

I only have the cumulative value. I need to get the total amount.

Can anybody help me inverse the cumulative amount, please?? 

Year                       Month                                              Cumulative                Total

2017	January	18	18
2017	February	28
2017	March	52
2017	April	68
2017	May	105
2017	June	137
2017	July	166
2017	August	192
2017	September	214
2017	October	242
2017	November	280
2017	December	313
2018	January	29	29
2018	February	52
2018	March	72
2018	April	91
2018	May	115
2018	June	137
2018	July	171
2018	August	205
2018	September	252
2018	October	334
2018	November	381
2018	December	419

[Johanno]

This might not be the best solution, but you could (with misspellings):

1. Create an index column in Power Query 1,2,3 etc.

2. Create a calculated column with the previous row:

Previousrow = 
VAR previousrow = CALCULATE(
                    SUM(Table1[Cumulative]);
                    FILTER(Table1;Table1[Index]=EARLIER(Table1[Index])-1)
)
RETURN
    previousrow

3. Create a measure that takes

Total = SUM(Table1[Cumulative])-SUM(Table1[Previousrow])

[Anonymous]

Thank you for your solution however in my case, the cumulative always starts in January.

[Johanno · Accepted solution]

Ok, than add an if statement in the calculated column to start over in january:

Previousrow = 
VAR previousrow = CALCULATE(
                    SUM(Table1[Cumulative]);
                    FILTER(Table1;Table1[Index]=EARLIER(Table1[Index])-1)
)
RETURN
    IF(Table1[Month]="January";0;previousrow)

[Anonymous]

Thank you for your help! You are amazing!