Cumulative line values for chart

HI ToKo ,

Did your table contain the original amount field? I'd like to suggest you use the following measure formula with original amount fields:

Measure = 
VAR currDate =
    MAX ( 'Table'[Date] )
VAR dateRange =
    CALCULATETABLE (
        VALUES ( 'Table'[Date] ),
        FILTER (
            ALLSELECTED ( 'Table' ),
            YEAR ( [Date] ) = YEAR ( currDate )
                && MONTH ( [Date] ) = MONTH ( currDate )
        )
    )
VAR total =
    CALCULATE (
        SUM ( 'Table'[Amount] ),
        FILTER (
            ALLSELECTED ( 'Table' ),
            YEAR ( [Date] ) = YEAR ( currDate )
                && MONTH ( [Date] ) = MONTH ( currDate )
        )
    )
VAR duration =
    DATEDIFF ( MINX ( dateRange, [Date] ), MAXX ( dateRange, [Date] ), DAY )
RETURN
    total / duration 
        * DATEDIFF ( MINX ( dateRange, [Date] ), currDate, DAY )

Regards,

Xiaoxin Sheng