In a recent post, C. Palo has asked for a "top N and others" solution. There is a KB article on the subject. But it's based on sets, which won't work for C. Palo because she has a few filters. So the top N will be dynamic while sets based approach only provides static top N, regardless of filters.

I would present here a tutorial on the topic. It is based on an approach by Tableau Zen Master Richard Leeke while using a different filter. Also would I explain some of the intricacies. This approach works on filtered results if any.

The example uses the superstore data set where we will show the top N countries with the highest sales, and group the others in a single bar.

Step 1. Create an integer parameter [Top N]
Step 2. Drag [Country / Region] to Details shelf and sort it by Sum(Sales) in descending order.
Note that all the 4 calculated fields below need to be set to compute using  [Country / Region].

Step 3. Create an Index: Index()
Turn it into discrete and drag it to Rows. Set it to compute using [Country / Region]. This index is mainly for the ordering of the results in final presentation.

Step 4. Create a [Top N+1 Rows] filter:

• Index()<=[Top N] +1

Drag it to Filters and set it compute using [Country / Region]. Select True at pop up.

We only need N+1 rows/bars/marks in the chart. There comes the filter. The (N+1)th row will show "Others" with its aggregated value.

Step 5. Create [Top Countries & Others]. This will alias the country at the (N+1)th position to be "Others". Drag it to Rows and set it to compute using [Country / Region].

• If Index()=[Top N] +1
• Then "Others"
• Else Attr([Country / Region])
• End

Step 6. Create [Top Sales & Others]. At the (N+1)th position, the value is altered to be an aggregated result. Drag it to Columns and set it to compute using [Country / Region].

• If Index()=[Top N] +1
• Then Window_Sum(Sum(Sales),0,Last())
• Else Sum(Sales)
• End

Note that in the above formula, the If statement sets the index=0 for the window function which has its own index. The settings here instructs the window function to compute from (N+1)th row to the last row.

The aggregation at the (N+1)th row can be the average of all the others if you wish:

• Window_Avg(Sum(Sales),0,Last())

We are done with a basic "Top N & Others" bar chart with grouping all others in one bar. Note that all table calculations have to compute using [Country / Region].
Dress up

Add a few extra steps to make the presentation better.

- Drag [Top Sales & Others] to Label/Text shelf and set it to compute using  [Country / Region].
- Create [Others] to color Top N and Others differently. Set it to compute using  [Country / Region].

• Index()=[Top N]+1

- In Step 5, add a little calculation to show # of countries in the "Others".

• If Index()=[Top N] +1
• Then Str(Size()-[Top N])+" Others" 

Here is the final result. The workbook can be downloaded here.