I've been wanting to learn more about the INDEX() function, this seemed like a good way to start. To get the top 1, all you need is an INDEX() with the table calculation appropriately partitioned. However, to show a top N and have them appropriately sorted I had to create a set to do the nested sort. I've attached a workbook (Tableau 7.0 format) that does this with the Superstore Sales data using a set to create the nested sort on Region/Customer and then using the INDEX() function to grab the top customer by # of sales in each region. I used these references to create the workbook:
Creating a nested sort:
How-to from Joe Mako on appropriately setting table calc fields:
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Also, here's an alternative method of calculation from an older file: http://www.tableausoftware.com/files/tips/pdf/TopSalesPerRegion.pdf
Thanks so much for your post! The 3rd link you posted was EXACTLY what I needed!
Have a great day!