Calculate the difference between yearly averages, for each individual user

[Anonymous]

The following is a sample user dataset where each user is assigned a rating at random times during the year (Some users are missing ratings for some of the years).

I have a matrix visual with the average rating per user, per year. (See example below). So John Smith had 2 enteries for the year 2020 and the matrix has a single average value for that user, for each year that they have data for.

What I'm trying to achieve is the Diff coloum (last coloum in 2nd visual), which is the difference between the 'latest average yearly rating' and 'earliest average yearly rating'. In Johns case this will be 1.225-0.936 (his value in 2021-2019). So "the earliest year" and "the latest year" with data could be different for each user. 

How can I calculate this coloum/ measure with DAX? 

Any help is much appreciated.

[smpa01 · Accepted solution]

@Anonymous  to be able to achieve this, you would need a Calendar Table. Once you have that, create a relationship between Fact[Date] and Calendar[Calendar_Date] which will look like below

 Then you can write the following meaure to achieve what you need

Measure = 
VAR _mxYear =
    CALCULATE (
        CALCULATE (
            MAX ( 'Calendar'[Calendar_Year] ),
            ALLEXCEPT ( 'Fact', 'Fact'[ID] )
        ),
        CROSSFILTER ( 'Fact'[Date], 'Calendar'[Calendar_Date], BOTH )
    )
VAR _minYear =
    CALCULATE (
        CALCULATE (
            MIN ( 'Calendar'[Calendar_Year] ),
            ALLEXCEPT ( 'Fact', 'Fact'[ID] )
        ),
        CROSSFILTER ( 'Fact'[Date], 'Calendar'[Calendar_Date], BOTH )
    )
VAR _minAvg =
    CALCULATE (
        AVERAGE ( 'Fact'[Rating] ),
        FILTER (
            VALUES ( 'Calendar'[Calendar_Year] ),
            'Calendar'[Calendar_Year] = _minYear
        )
    )
VAR _maxAvg =
    CALCULATE (
        AVERAGE ( 'Fact'[Rating] ),
        FILTER (
            VALUES ( 'Calendar'[Calendar_Year] ),
            'Calendar'[Calendar_Year] = _mxYear
        )
    )
RETURN
    _maxAvg - _minAvg

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[Anonymous]

Thank you @smpa01!  

[BeaBF]

@Anonymous Hi! 

Could you paste as a comment the table on which to calculate the required measurement?

Thx,

B.