Last Modified Date: 18 Dec 2017
AnswerThe below example can be found in the attached workbook, which uses the example data source Superstore.
Create a Calculated Field [LookupValue]
What this does is Index the columns, so that the far most right column is always 0
Create a Calculated Field [Across_Value]
What this does, is check each column for the value of LAST(). If it is 0 (The last column), then we sum the Measure amount, else, we have 0.
Create a Calculated Field [Rank]
What this does is Rank the SUM of the right most column in Tableau.
For the COMPUTE USING for RANK
Rank > Table Down
Across_Value > Table Across
Lookup > Month Then place the [Rank] field on the worksheet to the far most left as a discrete measure, and hide the header.