How to calculate differences in values between dates in rows within the same column

[DanielPasalic]

Hi all I have a problem to My tableDAX formula that did not worked.  There are 4 different columns: - date, id, Art.nr. and sold_item I would like to calculate differences in sold_item for products with same ID between dates (starting from oldest to latest date).  I tried in DAX with the calculated column but did not work.  Anyone who can give me advice on how to do it?

[Anonymous]

Should this not be calculated in Power Query? If this is not a dynamic calculation (and I doubt it is), please do it in PQ. Simpler, faster, more efficient.

[DanielPasalic]

sorry but I have no idea how to do it in Power Query

[Anonymous]

// This should be calculated in Power Query.
// I give you a DAX formula but if the table is
// big (and it seems to be a fact table), you
// might wait a very long time for this calculation
// to end. Depending on the size of the table
// you might even get a memory overflow. Then
// you know you have to do it in PQ. Let's say
// your table is T (I don't want to type the full name).
// By the way, using CALCULATE for a row-by-row
// calculation in a fact table will get you in
// trouble in no time.

sales_diff = // calc column
var __artikelNr = T[Artikelnr]
var __firstValue =
    SUMX(
        // I can use topn(1,...) here because
        // all rows with the same dates (ties)
        // will be returned. Same goes for the
        // other expression.
        topn(1,
            filter(
                T,
                T[Artikelnr] = __artikelNr
            ),
            T[Date],
            ASC
        ),
        T[Salt antal totalt]
    )
var __secondValue =
    SUMX(
        topn(1,
            filter(
                T,
                T[Artikelnr] = __artikelNr
            ),
            T[Date],
            DESC
        ),
        T[Salt antal totalt]
    )    
return
    __firstValue - __secondValue

[harshnathani]

Hi @DanielPasalic ,

https://community.powerbi.com/t5/Community-Blog/Getting-Previous-Values-in-Power-BI-Part-1/ba-p/1143...

Regards,

Harsh Nathani
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[Greg_Deckler]

@DanielPasalic  - See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/3395...