Scenario 1: Top N% by Number of Items

Option 1: Use level of detail (LOD) functions

LOD calculations allow for more flexibility in how the view is built, but the parameter requires manually setting all of the display values. These directions start from "Original View" in the workbook downloadable from the right-hand pane of this article. 

1. Click the down arrow next to the search bar and select Create Parameter...
2. In the Create Parameter dialog do the following, and click OK:
   1. Name the parameter. In this example, it's named "Select Top N Percentage (LOD)"
   2. For Data type, select Float
   3. For Display format, select Percentage
   4. For Allowable values, select Range
   5. Set Minimum to 0, Maximum to 1, Step size to .05
   6. Change Allowable values to List. This will populate the list with values
   7. Update the display values 1-N. For example, for .1 the display value should be 90%. This is necessary because the filter uses percentile, which requires the 1-N value.
3. Select Analysis > Create Calculated Field
4. In the Calculated Field dialog box that opens, do the following, and then click OK:
   1. Name the calculated field. In this example, the calculated field is named "Top N Customers by Sales (LOD) Filter"
   2. In the formula field, create a calculation similar to the following:

      { FIXED [Customer Name] : SUM([Sales])} 
      >=
      { FIXED : 
          PERCENTILE( { FIXED [Customer Name] : SUM([Sales])}, [Select Top N Percentage (LOD)])
      }

5. Drag [Top N Customers by Sales (LOD) Filter] to the Filters shelf
6. In the Filter dialog, check True and click OK

Option 2: Use table calculations 

These directions start from "Original View" in the workbook downloadable from the right-hand pane of this article. 

1. Click the down arrow next to the search bar and select Create Parameter...
2. In the Create Parameter dialog do the following, and click OK:
   1. Name the parameter. In this example, it's named "Select Top N Percentage"
   2. For Data type, select Float
   3. For Display format, select Number (custom) and add "%" as a suffix
   4. For Allowable values, select Range
   5. Set Minimum to 0, Maximum to 100, Step size to 1
3. Select Analysis > Create Calculated Field
4. In the Calculated Field dialog box that opens, do the following, and then click OK:
   1. Name the calculated field. In this example, the calculated field is named "Customer Rank by Sales"
   2. In the formula field, create a calculation similar to the following:

      RANK_UNIQUE(SUM([Sales]),'desc')

5. Create a calculated field named "Top N % Customer by Sales filter (# of items, table calc)" with a formula similar to

   [Customer Rank by Sales]
   <=
   WINDOW_MAX([Customer Rank by Sales])*([Select Top N Percentage]/100)

6. Drag [Top N % Customer by Sales filter (# of items, table calc)] to the Filters shelf
7. In the Filter dialog check True and click OK

Scenario 2: Top N% by Value

1. Click the down arrow next to the search bar and select Create Parameter...
2. In the Create Parameter dialog do the following, and click OK:
   1. Name the parameter. In this example, it's named "Select Top N Percentage"
   2. For Data type, select Float
   3. For Display format, select Number (custom) and add "%" as a suffix
   4. For Allowable values, select Range
   5. Set Minimum to 0, Maximum to 100, Step size to 1
3. Select Analysis > Create Calculated Field
4. In the Calculated Field dialog box that opens, do the following, and then click OK:
   1. Name the calculated field. In this example, the calculated field is named "Top N% Sales Filter"
   2. In the formula field, create a calculation similar to the following:

      RUNNING_SUM(SUM([Sales])) / TOTAL(SUM([Sales]))
      <=
      [Select Top N Percentage]/100

5. Drag [Top N% Sales Filter] to the Filters shelf 
6. In the Filters dialog, check True and OK