Arc Chart Tutorial

After years of using Tableau, I was finally given a use case that would allow me to create an Arc Chart; I always strive to build the best visualization for the client’s requirements. The client wanted to visualize the number of issues that were being escalated from each level. In this tutorial, I will go through the steps to create an Arc Chart.

Data

Our data set will consist of:

Copy and paste this into Tableau and look at the data.

Note: We could have used the left and right functions to isolate the level and then use Calculated Fields to work out the Start Point and End Point, but for simplicity we I will include this in the data set. But if you want to try, use something like IF LEFT([Step],1) = “A” THEN 1…

Calculated Fields

We will create a Path (bin) object by:

• Right click on Path
• Go to Create, Bins…
• In Edit [Path] set the Size of bins to 1
• Click Ok

Create the following Calculated Fields by as follows:

Index:

INDEX()-1

WC_PI:

WINDOW_MAX(MAX(PI()))

WC_End Point:

WINDOW_MAX(MAX([End Point]))

WC_Start Point:

WINDOW_MAX(MAX([Start Point]))

WC_Step Size:

([WC_End Point]-[WC_Start Point])/2

WC_Escalations:

WINDOW_MAX(MAX([Escalations]))

X:

((COS([Index]*[WC_PI]/180))*[WC_Step Size])

Y:

SIN([Index]*[WC_PI]/180)*[WC_Step Size]

Now that we have all the Calculated fields, we will now go about building our worksheet.

The Worksheet

Let’s start by dragging our Calculated fields onto the worksheet:

• Drag Step onto Detail Mark
• Drag Path (Bin) onto Columns
  • Right-click on Path (bin) to ensure the Show Missing Values is checked.
  • Drag Path (bin) onto the Details Mark
• Drag X onto Columns
  • Right click on X, select Compute Using and choose Path (Bin)
• Drag Y onto Rows
  • Right click on Y, select Compute Using and choose Path (Bin)
• Change the Mark Type to Line
• Drag Index onto the Path Mark
  • Right click on Index, select Compute Using and choose Path (Bin)
• Drag WC_Escalations onto the Size Mark
  • Right click on WC_Escalations, select Compute Using and choose Path (Bin)

You should now see the following:

Ok, we are not quite there yet, but we are getting there.

• Edit the X Calculated Field by changing it to:
  • ((COS([Index]*[WC_PI]/180))*[WC_Step Size])+[WC_Step Size]+[WC_Start Point]

This will shift the half circles and will give you the following:

nd we are done, at least from a technical perspective.

Now do the following:

• Remove Gridlines and other lines, so that we get a white background
• Fix the x-axis to be from 0.75 to 5.25
• Hide the X and Y Axis
• Add some tooltips
• Add Labels underneath the visualisation in a dashboard

In the end, hopefully, you will have something that looks like this.

his type of chart can be used to highlight:

• Time spent at each stage of a manufacturing process
• Drop-offs on during an online sales process
• Visitor drop-offs for views on a website

I hope you enjoyed following this blog and, as always, let me know your comments below, or on Twitter at @Tableau_Magic.

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