YOY week number

[RodrigoZD]

I would like to calculate a difference in averages if certain conditions are met:

In this particular example, my data looks something like this:

Then, when I group it by average of conditions (Year and WeekNumber), it looks something like this:

And finally, what I want to do, is to do an average when Year = Year -1 and week number is the same, so I would have something like this:

My approach was to create a formula that was something like:

Delta = CALCULATE ( AVERAGE ( Table[Ratio] ),
                                    FILTER( 
                                                 ALL ( Table ),
                                                 Table[Year] = Table[Year] - 1
                                                 && Table[WeekNumber] = Table[WeekNumber]
                                    )
               )
              // I know the WeekNumber = WeekNumber part is wrong since it's like 1=1, but 
             // I would like to know if there is a way to do something similar to this

[RodrigoZD · Accepted solution]

For those of you who could have the same question, I found a solution creating a measure like this:

DeltaTest = 
            CALCULATE(AVERAGE(Table[Ratio]),
            FILTER(
                    ALL(Table),
                    Table[WeekNumber] = SELECTEDVALUE(Table[WeekNumber]) && Table[Year] = SELECTEDVALUE(Table[Year])-1)
            )

and then just another measure that substract

Delta = Table[Ratio] - DeltaTest