Change in Values over Time - Calculated Column?

Hi,

Here is the result i got.  You may download my PBI file from here.

Hope this helps.

Okay, for anyone that comes across this thread in the future...  

Removal of the 'index' column was a bad idea. 

While it works without it, using the Date, as an index, memory consumption jumps through the roof.   So much so that with the addition of a couple more weeks of data my PC couldn't refresh.   And then, with a couple more weeks, the Power BI Service couldn't refresh.  

Here is the DAX with the Index column:  

QtyAvailableChange =
IF (
    ISBLANK (
        LOOKUPVALUE (
            Data[QtyAvailable],
            Data[Date], CALCULATE (
                MAX ( Data[Date] ),
                FILTER (
                    Data,
                    Data[Index] < EARLIER ( Data[Index] )
                        && Data[SKU] = EARLIER ( Data[SKU] )
                        && Data[Location] = EARLIER ( Data[Location] )
                )
            ),
            Data[SKU], Data[SKU],
            Data[Location], Data[Location]
        )
    ),
    0,
    [QtyAvailable]
        - LOOKUPVALUE (
            Data[QtyAvailable],
            Data[Date], CALCULATE (
                MAX ( Data[Date] ),
                FILTER (
                    Data,
                    Data[Index] < EARLIER ( Data[Index] )
                        && Data[SKU] = EARLIER ( Data[SKU] )
                        && Data[Location] = EARLIER ( Data[Location] )
                )
            ),
            Data[SKU], Data[SKU],
            Data[Location], Data[Location]
        )
)

Do it this way - not the way I previously referenced.   

To create the index column I added Index as a custom column in Query Editor with the M query: 

Index = Duration.Days(Date.From([Date])-#date(YYYY,MM,DD))

Where YYYY,MM,DD is the Year, Month and Day of my earliest Date record.