In week two we began our deeper dive into applying the many, many elements available within Tableau. An aspect that is valuable to know for highlighting and communicating whether a key target has been reached is Reference Lines or indicators. These allow the audience to clearly visualize how data values, regions, or ranges compare against the specified base or target value.
Reference Lines in charts are user-defined continuous vertical (Y-axis) or horizontal (X-axis) lines and include the option of Parameter Actions. A Parameter is a workbook variable that may be a date, numerical value or string that can replace a constant value in a calculation, filter, or reference line. Parameters are useful for adding interactivity and adaptability to a chart, such as when changing or updating target values, or enabling users to explore hypothetical ‘what-if’ scenarios.
Tableau allows you to provide multiple numbers or types of Reference Lines in addition to confidences intervals in a single graph if need be. Users may also apply Reference Bands, Reference Distributions or Reference Box Plots to charts as indicators as well (see below image).
Reference Distributions additionally allow for creating bullet charts, or for generating a shading gradient that may be arranged as quantiles, percentiles, percentages or standard deviation.
Types of Reference Indicators
Image Source: https://help.tableau.com/current/pro/desktop/en-us/reference_lines.htm
There are a few ways to add references lines, such as through the Analytics pane, the Analysis drop-down menu, or by right-clicking on the measure axis.
Our Case Studies:
The first example, using Tableau’s inbuilt Superstore Dataset, was to create a Reference Line using a parameter action. The line and its axis were selected through the Analytics Pane, as shown below.
Analytics Pane > Reference Line > Axis/Measure
Next, the surrounding regions and the dividing Reference Line were edited to suit the user preferences for line types, colour, etc.. A decision is made whether to apply the scope across tables, panes or cells.
Edit the Reference Line, Band or Box:
In the second example below, another approach was used. A Calculated Field is created before a Reference Line was applied via the Analytics Pane again.
Create a Calculated Field for a Selected Variable:
Add the Chosen Calculation:
In this example, an Average and then a Median Reference Line were added to this graph. A number of alternative Aggregations can be selected through Tableau, including Total, Sum, Constant, Minimum and Maximum.
The Final Chart Output:
For more on creating Reference Lines, Parameters and Calculated Fields, visit the Tableau Help website for the following sources:
Reference Lines, Bands, Distributions, and Boxes
Create Custom Fields with Calculations