Week over Week Change - CROSS YEARs

Hi, Anonymous 

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.

Table:

Date(a calculated table):

Date = 
ADDCOLUMNS(
    CALENDARAUTO(),
    "YearWeek",
    YEAR([Date])*100+WEEKNUM([Date])
)

There is a relationship between two tables. You may create a measure as below.

Result = 
var lastweeknum = 
CALCULATE(
    MAX('Date'[YearWeek]),
    FILTER(
        ALL('Date'),
        [YearWeek]<MAX('Date'[YearWeek])
    )
)
var lastweekamount = 
CALCULATE(
    SUM('Table'[Impressions]),
    FILTER(
          ALL('Date'),
          [YearWeek]=lastweeknum
    )
)
return
DIVIDE(
    SUM('Table'[Impressions])-lastweekamount,
    lastweekamount,
    0
)

Result:

Best Regards

Allan

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