Definition
Dual axis chart also known as combo chart is a combination of two or more charts into one chart.
e.g., combination of a bar and line chart.
Typically used to illustrate two or more measure fields e.g., profit and sales.
Example of a dual axis chart
Best practices for creating a dual axis chart.
Always show the axis clearly.
Use color, gridlines, and borders conservatively.
Avoid labelling the actual metrics as can lead to clutter.
Provide additional details on the tooltip.
Step by step guide on how to create a dual axis chart.
In this class, using data on Main type of roofing in Kenya, we will create a dual axis chart to compare use of ‘Asbestos sheets’ and ‘Corrugated iron sheets’ for different County’s. We will be creating a dual axis chart using a line chart and a bar chart.
Related: How to create a divergent bar chart.
Related: How to create a bar in bar chart.
Connect data on main type of roofing to Tableau app and follow the guideline below.
Step 1: Build a simple bar chart using measure field ‘Asbestos sheets’
Drag dimension ‘County' to the columns shelf.
Drag measure field ‘Asbestos sheets' to the rows shelf.
Resulting,
Step 2: Build a second bar chart using measure field ‘Corrugated iron sheets’
Drag measure field ‘Corrugated iron sheets’ to the rows shelf next to the field ‘Asbestos sheets’.
See resulting chart.
Step 3: Make the charts dual
There are two ways to achieve this;
Select the drop arrow of the field SUM(Corrugated iron sheets) in the rows shelf and choose ‘Dual Axis’.
or right click on the axis of the second chart ‘Corrugated iron sheets’ for this case, and select ‘Dual Axis’.
Note; Executing this step may change your chart from a bar to a circle, like in my case.
Step 4: Lets synchronize the axis
Right click on any of the two axes and select ‘Synchronize Axis’.
Note; Synchronizing your axis ensures the two charts use the same scale (hence this should be optional depending on how you would like to represent your data).
Executing we’ve;
Step 5: Change the charts to line and bar chart respectively
Under marks card, make the First chart a bar chart and the second chart a Line chart.
Executing above and removing one of the axis we’ve;
Tableau tip: How to select Top & Bottom N members using sets.
From this chart, we can easily compare use of ‘Corrugated iron sheets’ and that of ‘Asbestos sheets’ across all the counties. According to this data, ‘Corrugated iron sheets’ is used more than ‘Asbestos sheets’ across all the Counties.
Based on this data, dual axis chart is not the best chart to visualize this data since the variation between the two variables is huge. However, the data served its purpose - which is helping you learn how to create a dual axis chart in Tableau.
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