XYZ Analysis matching to a calendar

[Till__]

Dear all, I want to calculate an XYZ Analysis. This works quite fine, but in months where I do not sell a Artikel I do not have an entry conected to a date as it is not sold. But for my analysis I want this month to be counted with zero so that it is included into my Standard Deviation as well as in my average calculation. I was trying to circumvent the problem by matching the Artikel to a clalendar. 


XYZ Variation  =

VAR CalcTable =

    ADDCOLUMNS(

        CROSSJOIN(

            SUMMARIZE('Calendar', 'Calendar'[Year & Month (YYYY-MM)]),

            SUMMARIZE('Umsatz', 'Umsatz'[Artikel])

        ),

        "QuantityByMonth",

        CALCULATE(

            SUMX(

                Umsatz,

                COALESCE(Umsatz[UmsatzStück], 0)

            ),

            FILTER(

                Umsatz,

                Umsatz[Artikel] = EARLIER(Umsatz[Artikel]) &&

                YEAR(Umsatz[Zeit_Tag]) = LEFT(EARLIER('Calendar'[Year & Month (YYYY-MM)]), 4) &&

                MONTH(Umsatz[Zeit_Tag]) = RIGHT(EARLIER('Calendar'[Year & Month (YYYY-MM)]), 2)

            )

        )

    )

VAR Variation =

    DIVIDE(

        STDEVX.P(CalcTable, [QuantityByMonth]),

        AVERAGEX(CalcTable, [QuantityByMonth])

    )


Thank you all in advance! 

[Till__]

This code works for all the month the product has been sold but this is giving me a bias. Also the COALESCE(Umsatz[UmsatzStück], 0) does not help as the entry does not exist and is not blank. 

XYZ Variation =

VAR CalcTable =

    ADDCOLUMNS (

        SUMMARIZE ( 'Umsatz', Umsatz[Artikel],'Calendar'[Year & Month (YYYY-MM)]),

        "QuantityByMonth", CALCULATE ( SUMX( Umsatz, COALESCE(Umsatz[UmsatzStück], 0) ) )

    )

VAR Variation =

    DIVIDE (

        STDEVX.S ( CalcTable, [QuantityByMonth] ),

        AVERAGEX ( CalcTable, [QuantityByMonth] )

    )

RETURN

    IF (

        ISBLANK ( Variation ),

        BLANK (),

        IF ( Variation = 0, 1, Variation )

    )