Like the bar chart, the line graph was one of the original data visualizations introduced in William Playfair’s The Commercial and Political Atlas in 1786 and has remained a staple for data visualization practitioners to this day. The line graph plots points at the intersection of values on a vertical y-axis and horizontal x-axis and then connects those points with straight lines. Viewing the vertical location of values on the y-axis and how those values are changing from left to right on the x-axis makes the line graph ideal for analyzing trends over time.
As with the bar chart in Chapter 7, you can go about making a line graph in several ways in Tableau. To start, in Figure 8-1 I’ve double-clicked the Profit measure on the Data pane from the Sample – Superstore dataset. This action has placed the Profit measure on the Rows shelf with an aggregation of SUM, and the visualization has a mark type of Bar.
Figure 8-1. The default bar chart in Tableau, created by double-clicking the Profit measure from within the Data pane
My preferred method for creating a line graph is to right-click and drag my date dimension from the Data pane to the Columns shelf. I prefer this method because Tableau gives you the option to choose whether to use discrete date parts or continuous date values, as well as the granularity of the date (such as day, week, month, ...
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