A few days ago, one of our #MakeoverMonday Data Camp mates Jocelyn Ji created a viz based on radial bar chart. It looks interesting. So I dug into it and found the original approach is published by Toan Hoang. Tableau's product guru Bora Beran also created a similar chart a while ago.

I found that the calculation of the chart can be made a bit easier:
- all (nested) table calculations only need to compute along a single dimension.
- shorter bars need fewer data marks. Total data marks are reduced.

Here is my approach, based on the same data set as Hoang's, with an extra column Type. This table can be generated using Union or Cross Join from the original data.
Path is created from Type. The largest value will have 271 data marks. The smaller values will have less marks, in proportion to the Values. The previous solutions need a uniform number of data marks for each bar, no matter what the bar size is.

Path is defined as such where each bar has a different number of data marks. The largest has 271 marks. 271 is an artificial number. We may give a different one if we wish. The bigger the number, the smoother the curve.

• CASE  [Type]
• WHEN 1 THEN 0
• WHEN 2 THEN [Value]*270/{MAX([Value])}
• END

Format Path as Integer. Then Create a bin on Path with step size 1.

To trigger data densification by Path bin:
- Drag it to the Rows, right click it and select Show Missing Values
- Then drag it to the Path shelf of line chart data mark.
- Note in our example, at the bottom-left corner, the number of data marks is showing 731 from initial 10.

The calculated fields are created as follows:
- Pi = Window_Max(Max(Pi()))   //Pi for every data point.
- Rank = Rank_Unique(-Sum(Value))  //Reverse rank as radius.
- Rank Max = Window_Max(Rank)  //Rank available at every data point.

Coordinates are calculated as follows, the same as those of a circle:
- X = COS((Index()-1)*[Pi]/180)*[Rank Max]
- Y = SIN((Index()-1)*[Pi]/180)*[Rank Max]

The first 3 calculated fields are nested within X and Y. We need to edit the table calculations of X and Y to set up those for each of the nested fields.