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rsbin's avatar
rsbin
Community Champion
6 years ago
Solved

Moving Average -> Standard Deviation

Good Morning,

Reaching out to the DAX experts out there.  I am trying to calculate the Standard Deviation of a Measure based on a 3 Day Moving Average (i.e. 3DayStdDev_EquipIDRatio).  My sample data looks like this:

DateGSIndexEquipmentIDCountTotalVisitsEquipmentIDRatio
8/1/201913079135550.227
8/2/201922931135240.217
8/3/20193103749970.208
8/4/2019463733260.192
8/5/20195232686190.270
8/6/201962908145990.199
8/7/201972994143830.208
DateGSIndex3DayEquipID3DayVisits3DayStdDev_EquipIDRatioStd. Dev Excel
8/1/20191    
8/2/20192    
8/3/2019370473207600.0080
8/4/2019446052184700.0104
8/5/2019540001694200.0338
8/6/2019658712654400.0353
8/7/2019782283760100.0314

 

EquipIDCount , TotalVisits and Equipment IDRatio are all Measures.

EquipIDRatio is a measure  - simply (EquipIDCount / TotalVisits).

3DayVisits and 3DayEquipID are moving average calculations wherein I use the Index to Sumx the 3 values (Current Day +2 prior days). 

I am able to calculate Standard Deviation on my database as a whole using this DAX provided by Greg_Deckler and az38 

 

 

 

StdDev_EquipIDRatio = 
VAR _table = SUMMARIZE(FILTER(GeneralStatistics, GeneralStatistics[TotalVisits] <> 0),[Date],"_EquipIDRatio",[EquipmentIDRatio])
RETURN STDEVX.P(_table,[_EquipIDRatio])

 

 

 

The Standard Deviation in the last column was calculated in Excel.  This is the number I am trying to replicate in DAX.  This number is the Standard Deviation of the EquipmentIDRatio of the current day + the previous 2 days.

So on day 3, I need to take the Ratio values from Day 1 - 3

On day 4, I need to take the Ratio values from Day 2 - 4. And so on.....

Since EquipIDRatio is a measure, to calculate Std Dev.,  I need to construct a virtual table as I have done above, but containing only the 3 relevant values for each Date or Index.  I have hit a wall and unable to figure out the correct way to do this in DAX.

Hoping one of you can point me in the right direction.

Thanks in advance and best regards,

 

Need Help
  • Icey's avatar
    Icey
    6 years ago

    Hi rsbin ,

     

    How about using ALLSELECTED in the expression?

    3DayStdDev_EquipIDRatio =
VAR CurrentIndex =
    MAX ( GeneralStatistics[GSIndex] )
VAR PreviousIndex = CurrentIndex - 2
VAR _table =
    SUMMARIZE (
        FILTER (
            ALLSELECTED (GeneralStatistics ),   ------------------edited
            GeneralStatistics[TotalVisits] <> 0
                && GeneralStatistics[GSIndex] >= PreviousIndex
                && GeneralStatistics[GSIndex] <= CurrentIndex
        ),
        [Date],
        "_EquipIDRatio", [EquipmentIDRatio]
    )
RETURN
    STDEVX.P ( _table, [_EquipIDRatio] )

     

     

    Best Regards,

    Icey

     

    If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

4 Replies

  • Icey's avatar
    Icey
    Community Support
    6 years ago

    Hi rsbin ,

     

    How about this?

    3DayStdDev_EquipIDRatio =
VAR CurrentIndex =
    MAX ( GeneralStatistics[GSIndex] )
VAR PreviousIndex = CurrentIndex - 2
VAR _table =
    SUMMARIZE (
        FILTER (
            GeneralStatistics,
            GeneralStatistics[TotalVisits] <> 0
                && GeneralStatistics[GSIndex] >= PreviousIndex
                && GeneralStatistics[GSIndex] <= CurrentIndex
        ),
        [Date],
        "_EquipIDRatio", [EquipmentIDRatio]
    )
RETURN
    STDEVX.P ( _table, [_EquipIDRatio] )

     

     

    Best Regards,

    Icey

     

    If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

    • rsbin's avatar
      rsbin
      Community Champion
      6 years ago

      Good Morning Icey 

      Thanks much for the reply.   I have attempted that code as as Solution, but it returns only an answer for the last date.

       

      The ".03142" is the correct answer for Index = 7.   I too thought it would cycle through and provide an answer for each Index, but as you can from the above, it Returns just a single value.

      I got up this morning thinking "CALCULATETABLE" might be the way to proceed.   Really appreciate you taking the time to respond. If you have further suggestions I would be grateful to hear them.  Kudos for the attempt.

       

      Kind Regards,

      • Icey's avatar
        Icey
        Community Support
        6 years ago

        Hi rsbin ,

         

        How about using ALLSELECTED in the expression?

        3DayStdDev_EquipIDRatio =
VAR CurrentIndex =
    MAX ( GeneralStatistics[GSIndex] )
VAR PreviousIndex = CurrentIndex - 2
VAR _table =
    SUMMARIZE (
        FILTER (
            ALLSELECTED (GeneralStatistics ),   ------------------edited
            GeneralStatistics[TotalVisits] <> 0
                && GeneralStatistics[GSIndex] >= PreviousIndex
                && GeneralStatistics[GSIndex] <= CurrentIndex
        ),
        [Date],
        "_EquipIDRatio", [EquipmentIDRatio]
    )
RETURN
    STDEVX.P ( _table, [_EquipIDRatio] )

         

         

        Best Regards,

        Icey

         

        If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.