Toan Hoang

Creating Gradient Half Circle Charts in Tableau

Toan Hoang

Recently, I explored the idea of gradients in my Gradient Bar Chart tutorial. After release, I was asked to explore gradients a bit more, so I decided to look at circles and to revisit an old favourite of mine, and in this tutorial, we will create Gradient Half Circle Charts in Tableau.

Note: This is an alternative type of data visualisation, and sometimes pushed for by clients. Please always look at best practices for data visualisations before deploying this into production.

Apart from double densification and a very cool look, I really think this is a for fun data visualisation, maybe in an infographic.

Data

We will start by loading the following data into Tableau.

Category,Value
Category B,80
Category A,100

Once your data is loaded into Tableau, right-click on the data source and click on Edit Data Source… with the Data Source Editor open, paste the following:

Circle,Path
0,0
0,100
180,0
180,100

Note: If you are using Tableau 2020.2 or great i.e. have access to new Relationship Model, you will need to double-click on the originally pasted data source to open up before pasting in the Path Data.

You should get an error as there is no joining column, however, click on Add new join clause, go to Create Join Calculation, type 1 and click OK. Do this for the right-hand side as well. Ensure that you have Inner join selected and you should see the following:

Note: we need additional records as we are going to be drawing lines and using densification to get more points on our canvas. For more information, check out our article on Data Densification.

Calculated Fields

With our data set loaded into Tableau, we are going to create the following Bin and Calculated Fields:

Path (bin)

Circle (bin)

Index

(INDEX()-1)/2

Note: This will be used to draw half circle lines.

Distance

INDEX()-1

Note: This will be used to draw increasingly larger lines.

Category Index

IF INDEX() = 1 THEN
    -1
ELSE
    1
END

Note: This will be used to flip the circle around.

TC_Value

WINDOW_SUM(SUM([Value]))

X

SIN(RADIANS([Index]))*[Distance]*[TC_Value]*[Category Index]

Y

COS(RADIANS([Index]))*[Distance]*[TC_Value]

TC_Color

[Category Index]*[Index]

With this done, let us start creating our data visualisation.

Worksheet

We will now build our first worksheet:

If all goes well, you should see the following:

We are going to do some serious editing of the Table Calculations to achieve our desired effect, follow very carefully:

We should now have the following:

We will now edit the Table Calculation for Y:

We are getting closer, and we should now see the following:

Now we are going to adjust the colour:

You should now see the following:

And now we are pretty much done with our Gradient Half Circles, however, we will need to adjust the cosmetics:

You will want to end with something like the following:

and boom, we are done! I hope you enjoyed this tutorial, and as always, you can find this data visualisation on Tableau Public at https://public.tableau.com/profile/toan.hoang#!/vizhome/GradientHalfCircles/GradientHalfCircles

Summary

I hope you all enjoyed this article as much as I enjoyed writing it and as always do share the love. Do let me know if you experienced any issues recreating this Visualisation, and as always, please leave a comment below or reach out to me on Twitter @Tableau_Magic. Do also remember to tag me in your work if you use this tutorial.

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