1/1/2015
Node-Link Tree Diagram in Tableau


Back in November someone from Zurich, Switzerland, emailed me about using my sankey-style slopegraph technique in Tableau to emulate a chart in D3. The diagram is often referred to as a node-link tree diagram. To build this I utilized the same technique as outlined here. I posted an image on Twitter back in November here but the data used to build this was proprietary so I wasn't able to post the workbook. I anonymized the data and the Tableau workbook is now posted here

   

The primary difference in this approach vs. the original sankey-style slopegraph (here and here) is that there are multiple levels. In the original design the field T goes from -6 to 6 in increments on .25. In this workbork there is a new field T2 which is equal to T + 12 for level 2 and T + 24 for level 3.

   Root Node to Level 1: T = -6 to 6
   Level 1 to Level 2: T = 6 to 18
   Level 2 to Level 3: T = 18 to 30

An alternative approach: Create a field for each level and then set T2 = T +12 or +24 based on the level.

Below is an image of the same visualization with the axis labels and gridlines to show how this approach works.

   
The created a dual axis to create the circles on the nodes, changing the second Marks to Circles instead of Lines. I created a calculated field for Color (optional) so that each node level would be a different color:

   Calculated Field Name: Color
   Formula:
      if sum([T2])= -6 then 'gray'
      elseif sum([T2])= 6 then 'orange'
      elseif sum([T2])= 18 then 'blue'
      elseif sum([T2])= 30 then 'green'
      end

Once the first chart is complete simply swap the rows and columns and reverse the scale on the Y-Axis (T2) to have the chart go down instead of across.


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I hope you find this helpful. If you have any questions feel free to email me at Jeff@DataPlusScience.com.


Jeffrey A. Shaffer

Follow on Twitter @HighVizAbility