getting previous week value

You have to use all

var prev week value =
CALCULATE(
SUM('table'[value]),
FILTER(all('table'),'table'[yearweek]=previousweek)
)
return prev week value

It is better to take week to a different table or preferably to date table. Create a rank.

Week rank = Rank(Week,Week[yearweek],,asc,dense)

var prev week value =

Var previousweekRank= maxx(Week,Week[Rank])-1
CALCULATE(
SUM('table'[value]),
FILTER(all('Week'),'Week'[Rank]=previousweekRank)
)
return prev week value

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Hi  VladMatao ,

You have to modify your measure as below:

Measure =
VAR previousweek =
    IF (
        MOD ( SELECTEDVALUE ( 'table'[yearweek] ), 100 ) = 1,
        SELECTEDVALUE ( 'Table'[yearweek] ) - 49,
        SELECTEDVALUE ( 'Table'[yearweek] ) - 1
    )
VAR prevweekvalue =
    CALCULATE (
        SUM ( 'table'[value] ),
        FILTER ( ALL ( 'Table' ), 'table'[yearweek] = previousweek )
    )
RETURN
    prevweekvalue

Finally you will see:

For the related .pbix file,pls click here.

v-kelly-msft amitchandak 

I think this one doesn't work because the "cat_type" and "category" will change, and if I want to show it for certain category types for example will give me the wrong value. I managed to do it with a column:

lastweekvalue = CALCULATE(SUM('table'[value]),FILTER('table',EARLIER('table'[category])='table'[category] && EARLIER('table'[KPI_type])='table'[KPI_type] && EARLIER('node'[cat_type])='table'[cat_type] && EARLIER('table'[year week])='table'[year week]+if(MOD('table'[year week],100)=52,49,1)))

 But I would still like to know if this is possible with a measure