Substracting data for proper visualization

hi MKPartner 

First get the number equivalent of your week (not wk42, 43) as you will have trouble comparing those weeks if week numbers aren't always in "00" format. For example Wk10 is next to Wk1 alphabetically. You should be able to get that in the query editor by duplicating your week colum and then replacing WK with nothing for the duplicate. Once you have that, create this measure:

VAR _prevWk =
    CALCULATE (
        [sum of value],
        FILTER (
            ALL ( 'table'[wk number] ),
            'table'[wk number]
                = MAX ( 'table'[wk number] ) - 1
        )
    )
RETURN
    [sum of value] - _prevWk

Otherwise please provide a workable sample data (not an image), your expected result from the same sample data and your reasoning behind. You may post a link to Excel or a sanitized copy of your PBIX stored in the cloud.