Window_stdev table(across) along with date in power BI

[asdf1608]

I am trying to convert tableau dashboard to poewr BI. I am facing an isssue in converting a calculated column called window_stdev.

The formula in tableau is : 

WINDOW_STDEV(SUM([Quantity 2])).

It seems to be calculating table across specific dimension by date

The result from tableau is

The formula I used in power BI  : 

Rolling Stdev =

VAR CurrentRowDate = aa[Date]

VAR RowsToInclude =

    FILTER(

        ALL(aa),

        aa[Date] >= (CurrentRowDate - 2) && aa[Date] <= CurrentRowDate

    )

RETURN

IF(

    COUNTROWS(RowsToInclude) > 1,

    STDEVX.P(RowsToInclude, aa[Quantity2]),

    BLANK()

) // this is not giving me correct answer.

The above formula is not giving me the answer same as tableau

The result from power BI is

I am attaching the excel file and poewr BI file

sample.XLSX

Sample.pbix

Help in this is really needed.

Thanks in advance

[lbendlin]

Your sample table "aa"  has 213K rows, but only 18K distinct rows.  What are all these duplicates?

Are you sure you want to calculate the standard deviation across three values only?  That will be statistically useless.

[asdf1608]

@lbendlin 

certain id may repeat. I need the standard deviations for the window across date.

normal standard deviation is coming in power BI. But for the windows it is giving me an wrong answer

[lbendlin]

Where is this filter 

 FILTER(

        ALL(aa),

        aa[Date] >= (CurrentRowDate - 2) && aa[Date] <= CurrentRowDate

    )

in Tableau?  From your example WINDOW_STDEV calculates across all dates for each ID.

[asdf1608]

@lbendlin There are no filters. As you said WINDOW_STDEV calculates across all dates for each ID.

I just used the above DAX. It might be wrong.

That's why I raised this. 
I am not sure why to create DAx so that the values matches with Tableau

[lbendlin]

How do you know the Tableau values are correct?

[asdf1608]

@lbendlin 

I am not sure if the tableau result is correct. All I want is the formula conversion.

Window_stdev to be calculated across the specified dimension

WINDOW_STDEV(SUM([Quantity 2])).

It seems to be calculating table across specific dimension by date

Please help me in this

Thanks in advance

[asdf1608]

@lbendlin 

I am not sure if the tableau result is correct. All I want is the formula conversion.

Window_stdev to be calculated across the specified dimension

WINDOW_STDEV(SUM([Quantity 2])).

It seems to be calculating table across specific dimension by date

Please help me in this

Thanks in advance