Trying to calculate quartiles in MDX

Question

My data looks like this:

ID                                   |PersonID  |CompanyID  |DateID  |Throughput |AmountType
33F467AC-F35B-4F24-A05B-FC35CF005981 |7         |53         |200802  |3          |0
04EE0FF0-511D-48F5-AA58-7600B3A69695 |18        |4          |201309  |5          |0
AB058AA5-6228-4E7C-9469-55827A5A34C3 |25        |69         |201108  |266        |0

with around a million rows. The columns names *ID refers to other tables, so they can be used as dimensions.

I have an OLAP cube with the column Throughput as Measure and the rest as dimensions.

I want to calculate Quartile 1 and 3 of the Throughput measure.

I followed this guide: https://electrovoid.wordpress.com/2011/06/24/ssas-quartile/ together with this post: Calculating Quartiles in Analysis Services

From those I tried to use this MDX query:

WITH
SET selection as ([Dates].[Year].&[2014],[Dates].[Month].&[1])  

SET [NonEmptyIds] AS
 NonEmpty(
      [ThroughputID].[ID].[id]
   *[ThroughputID].[ID].[Id].ALLMEMBERS
  ,
  {[Measures].[Throughput]} * [selection]
 )
 SET [ThroughputData] AS 
ORDER
    (    
        [NonEmptyIds],  
        [Measures].[Throughput], 
        BASC
     )
MEMBER [Measures].[RowCount] AS COUNT (ThroughputData)
MEMBER [Measures].[i25] AS ( .25 *  ( [RowCount] - 1 ) ) + 1
MEMBER [Measures].[i25Lo] AS FIX([i25])   - 1
MEMBER [Measures].[i25Rem] AS ([i25] - FIX([i25]))
MEMBER [Measures].[n25Lo] AS (ThroughputData.Item([i25Lo]), [Throughput])
MEMBER [Measures].[n25Hi] AS (ThroughputData.Item([i25Lo] + 1), [Throughput])
MEMBER [Measures].[Quartile1] AS [n25Lo] + ( [i25Rem] * ( [n25Hi] - [Throughput] ))

SELECT
selection ON 0,
[Measures].[Quartile1]
ON 1
FROM (SELECT [Dates].[Y-H-Q-M].MEMBERS ON 0 FROM [Throughput])

But I get: 'Query (6, 7) The ID hierarchy is used more than once in the Crossjoin function.'

I am quite new to OLAP and MDX. Any ideas what's wrong and how I should calculate the quartiles correct?

I read somewhere that I needed the ID dimensions to be able to get a set with all values instead of aggregated values when calculating Quartiles...

Answer 1

Culprit is the following piece of code:

SET [NonEmptyIds] AS
 NonEmpty(
      [ThroughputID].[ID].[id]
   *[ThroughputID].[ID].[Id].ALLMEMBERS
  ,
  {[Measures].[Throughput]} * [selection]
 )

You can't use the same hierarchy more than once in the cross-join. Here you have used [ThroughputID].[ID] twice. Instead try the below:

SET [NonEmptyIds] AS
 NonEmpty(
      [ThroughputID].[ID].[Id].ALLMEMBERS
  ,
  {[Measures].[Throughput]} * [selection]
 )