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Hat Graph






Tableau Canvas Layout:





Jessia K. Witt wrote an article entitled Introducing Hat Graphs. The hat graph was created as an alternative to paired bar charts. In this article, she discusses their potential usefullness and the results of five empirical studies.


Data Set: Lollipop Data



Building a Hat Graph


Step 1: Create a Paired Bar Chart


   Double-click Quantity to put it on Rows or drag it Rows.
   Double-click Region to put it on Columns or drag it Columns.
   Double-click Ship Mode to put it on Columns or drag it Columns.
   Drag Ship Mode to Filters and select First Class and Second Class by unchecking Same Day and Standard Class.
   Select Analysis from the top menu, then select Totals and then select Add All Subtotals.
   Select one of the Total Bars. A small tooltip box should popup with "Automatic" shown with a dropdown arrow. Click the dropdown arrow and select Hide. This will hide the Total bars and reset your axis.
   Right-click on the Total label on the X-Axis and select Format.
   In the Format Pane on the left-hand side, delete the word "Total" from th Totals Label.
   In the Format Pane on the left-hand side, click the fourth icon at the top for Borders and set the Column Divider to "None".
   In the Format Pane on the left-hand side, click the fifth icon at the top for Lines and select the Rows tab and set the Grid Lines to "None".
   Click Size on the Marks Card and adjust the size slider to maximize the size of the bars.
   Drag Ship Mode to Color on the Marks Card to change the color of the bars as needed (optional).

You should now have a paired bar chart that looks something like this.


Step 2: Create the Hat Graph


There are two parts to the hat graph. First, we need to convert the first bar into a line placed at the top of the first bar. Second, we replace the second bar with a partial bar starting at that same position and graphing the difference between the first and second bar. In Tableau, we will do this with the Gantt mark and a calculated field.

   Calculated Field: Difference in Quanity
   Formula: -SUM([Quantity]) + LOOKUP(SUM([Quantity]),-1)

   On the Marks Card, change the Mark Type to Gantt
   Drag Difference in Quanity to Size.
   Remove Ship Mode from Color on the Marks Card if you used color.
   Click Color on the Marks Card and set the color to the desired color. I used hex color #1ba3c6.
   Set the Border Color to the same color.

You should now have a Hat Graph that looks like this.




Adding Labels


Adding labels to a hat graph might be useful. First, let's add a label on the difference value. To do this, we will create another calculated field for the Difference Label.

   Calculated Field: Difference Label
   Formula: SUM([Quantity]) - LOOKUP(SUM([Quantity]),-1)

   Drag Difference Label to Label.
   Select Label on th Marks Card and format the text to be horizontal and vertical center. Adjust the font as needed.

The hat graph with a single label looks like this.




You can leverage a dual axis to add additional labels for the total of each category.

   Drag Quantity to the Rows.
   Right-click Quantity on the Rows and select Dual Axis.
   Right-click on the secondary y-axis and select Syncronize.
   On the dropdown box in the Marks Card, change the Mark type to Bar.
   Drag Quantity to Labels on the Marks Card.
   Select Label on th Marks Card and format the text to be horizontal center and vertical top. Adjust the font as needed.
   Select Color on th Marks Card and set Opacity to 0% and Border to None.





Related Material:


Introducint Hat Graph by Jessia K. Witt
How to Add Top and Bottom Borders to Gantt Charts in Tableau by Viz Simply


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