Sparklines are one of my favorite chart types to include in dashboards, yet I see many people using them without providing enough context. Some people like to add bandlines, some like to add sets of dots, some like to add text, all in an effort to add meaning to sparklines. These are perfectly fine, but I think there’s a better way to make sparklines actionable. Is this the best way? Maybe not, but it is an alternative worth considering.
Sparklines were first introduced by Edward Tufte in his book Beautiful Evidence. Tufte says: “A sparkline is a small intense, simple, word-sized graphic with typographic resolution.” Stephen Few expands Tufte’s definition in his book Information Dashboard Design: “Their whole purpose is to provide a quick sense of historical context to enrich the meaning of the measure. This is exactly what’s required in a dashboard.”
When someone is creating a dashboard, they should provide as much information and meaning as possible to make the information actionable. I don’t see any examples from Tufte, Few or Jim Wahl that provide much meaningful context to the end of a sparkline.
Tufte provides some examples:
He might add a red dot to the end of the line along with some text to highlight the latest value.
While it’s a bit tough to see in this next example, Tufte has used red dots for the beginning and ends of the lines and blue dots to indicate the highest and lowest values.
It’s important to also note how Tufte always includes the values associated with all of the highlighted dots.
Few says: “Meaningful context has been added to these metrics in the form of sparklines, which provide a quick sense of the history that has led up to the present.” This small section of a dashboard is a classic Few design. You’ll often see him use (1) sparklines, (2) a visual indicator of health (the red dots in this case), and (3) bullet charts closely together.
When I use sparklines, I like to combine all of the elements of Tufte and Few designs. Let’s look at an example.
On the left you see the sparklines, but notice that I use the dot on the end of the line as an indicator to take action. Tufte uses the dot one the end to indicate you’re at the end. Does that make it actionable? Not necessarily. Few separates the indicator into its own space and does not mark the end of the sparkline. My version saves space, increases the data-to-ink ratio, and provides a visual indicator to the reader in one chart.
The table to the right summarizes the sparkline, pulling from Tufte’s practices. In this example, I’m concerned with comparingthe last two 7-day periods. Notice how I used conditional formatting so that the dot on the end of the line is the same color as the text in the WoW and WoW% columns. I don’t use bullet graphs because I feel that the text itself is sufficient; I don’t want to add a graph for the sake of having a graph for everything.
Simple, concise, actionable…all things you want in a dashboard. Keep reading to see how I built these sparklines in Tableau.