Sparklines—Deceptively Simple

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Sparklines, intense, word-sized line graphs, are popping up just about everywhere and for good reason. A lot of information can be packed in a space of about 15 characters wide by 2 to 3 characters high, saving on precious screen real estate in dashboards and graphic visualizations. But like any other visualization, the use of sparklines needs to be well thought out in order to provide meaningful insight instead of just taking up space or, worse, misleading the user.

Consider the Content

First and foremost, the data itself must be conducive to being shown as a line graph. Line graphs usually show data over time, but they can also be used to show other trends such as an occurrence of a phenomenon over distance. For some this is completely obvious, but not so for everyone. I recently saw a sparkline that showed current period revenue by geographic location. Clearly the creator wanted to show the information in a small space, however, this data would have been better shown as a bar graph. The data is discrete and lines connecting the data points are totally meaningless causing the reader to spend time trying to make sense of something that doesn’t make sense.

sparklinesEqually important is the presentation of the actual visualization. Is the sparkline spread out over 8 character widths or 15? How tall is it? Seem trivial? Not by a long shot. If the data is shown as a wide sparkline that is not very tall, important variations in the data may not be visible. On the other hand, if the sparkline is too tall, the data may appear spikey and convey a lot of “noise.” Visualization guru, Edward Tufte, suggests that the best dimensions for the sparkline, or aspect ratio, yield slopes of 45 degrees over the cycles in the time series. He suggests that the best sparklines are not smooth or spikey, but lumpy.


Consider the Context

Like nearly all data, the data in sparklines is most meaningful when shown in some kind of context. Depending on the focus of your findings, you can show two or more sparklines on the same graph to show a comparison. It is also very common to show a series of sparklines. For instance, if you have 5 products and 5 geographic locations, you may want to show a chart of 25 sparklines in five rows and five columns, each showing the sales of an individual product and location, over the same time period. When showing a series of related sparklines, you will want to make all of the sparklines the same size and use the same aspect ratio. Since sparklines do not generally show any axis values, it might be necessary to call out one number on each sparkline such as current month sales.

You can include a surprising amount of information on a sparkline or series of sparklines. For instance, you can highlight the high and low data points with a colored dot. You can overlay your sparkline with a lightly tinted bar to show the normal range or with a colored line to show the target. Or you can include sparklines in a chart with other data. You can add light vertical lines to demarcate time periods. There is an endless variety of tailoring that you can do to convey more information. But you need to think through the visualizations very carefully to ensure that every mark you add conveys more information and does not confuse the reader.

Edward Tufte and information design expert, Stephen Few, agree on the importance of simplicity and the need to eliminate optical clutter. Avoid outlining graphs. Avoid color that doesn’t mean anything. Avoid special effects like 3D and texturizing. No axes alongside of your sparklines. No labels. Just data.

BIO Business Intelligence gives your users self-service, interactive reporting through our popular viewer or the optional viewer of your choice, giving you the ability to present all of your company’s data in any of the traditional or newest visualizations. Choose sparklines or bubble graphs or tree maps or bullet graphs, but choose wisely and carefully consider every aspect of your presentation so you convey the most information for the best analyses and decision making.

Click here for a link to Edward Tufte’s forum entry, Sparkline Theory and Practice.

Join BIO for a free webinar to get a feel for the extensive out-of-the-box content offered in BIO business intelligence software. And please contact me at 203.705.4648 or by email at if you have any questions about BIO or business intelligence in general.

By Sandi Richards Forman of BIO Analytics, Corp., Microsoft Dynamics Business Intelligence (BI) Solution Provider

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