Iterative Stock Cover Calculation

Hi Anonymous

Here is an example pbix showing one way to do the calculations.

PBIX link

I put a table in the PBIX showing the key figures:

Generally, when you have Sales/Production data and you want to derive balances at any point in time, you need to create a series of cumulative calculations. 

In this case I started with a table pretty much as you described. Opening Value exists only in the first week.

Then created a set of base measures (Opening, Production, Sales) and corresponding cumulative measures.

Opening = 
SUM ( Forecast[Opening Value] )

Production = 
SUM ( Forecast[ProductionPlan] )

Sales = 
SUM ( Forecast[SalesForecast] )

Cumulative Opening = 
VAR MaxWeek =
    MAX ( Forecast[Week] )
RETURN
    CALCULATE ( [Opening], Forecast[Week] <= MaxWeek + 1 )

Cumulative Production = 
VAR MaxWeek =
    MAX ( Forecast[Week] )
RETURN
    CALCULATE ( [Production], Forecast[Week] <= MaxWeek )

Cumulative Sales = 
VAR MaxWeek =
    MAX ( Forecast[Week] )
RETURN
    CALCULATE ( [Sales], Forecast[Week] <= MaxWeek )

Then created Closing/Opening balance measures, representing "stock" on hand at the end/start of each week:

Balance Closing = 
[Cumulative Opening] + [Cumulative Production] - [Cumulative Sales]

Balance Opening = 
VAR MaxWeek =
    MAX ( Forecast[Week] )
RETURN
    CALCULATE ( [Balance Closing], Forecast[Week] = MaxWeek - 1 )

Then the Cover measure makes use of the above measures.

Cover =
VAR BalanceOpening = [Balance Opening]
VAR MaxWeek =
    MAX ( Forecast[Week] )
VAR FutureWeeks =
    FILTER ( ALL ( Forecast[Week] ), Forecast[Week] >= MaxWeek )
VAR PreviousSalesCumulative =
    CALCULATE ( [Cumulative Sales], Forecast[Week] < MaxWeek )
VAR FutureSales =
    GENERATE (
        FutureWeeks,
        VAR SalesInWeek = [Sales]
        VAR FutureSalesCumulative = [Cumulative Sales] - PreviousSalesCumulative
        VAR FutureSalesCumulativePre = FutureSalesCumulative - SalesInWeek
        RETURN
            ROW ( "WeekIndex", Forecast[Week] - MaxWeek,
            "SalesInweek", SalesInWeek,
            "FutureCumulativeSales", FutureSalesCumulative,
            "FutureCumulativeSalesPre", FutureSalesCumulativePre )
    )
VAR CoverResult =
    MINX (
        FutureSales,
        IF (
            [FutureCumulativeSales] >= BalanceOpening
                && [FutureCumulativeSales] - [SalesInweek]
                <= BalanceOpening,
            [WeekIndex]
                + DIVIDE ( BalanceOpening - [FutureCumulativeSalesPre], [SalesInWeek] )
        )
    )
RETURN
    CoverResult

This particular measure finds the earliest week where the Opening Balance is exhausted by future sales, then calculates the fractional week index where this occurs. The FutureSales variable stores the key values used in the calculation, then CoverResult finds the appropriate row and does the final calculation (using MINX). The above code could well be improved!

Regards,

Owen