Should you have a Horizon Graph for your dashboard? When a new information visualization technique is invented, it’s interesting news. The ones that are worthwhile find themselves in our mental toolboxes and eventually on our dashboards. Sparklines, bullet graphs, treemaps come to mind as recent inventions of note.
When a new infomation visualization technique comes out and is lauded by Stephen Few, however, then it becomes not just interesting, but important! Stephen Few, author of Information Dashboard Design: The Effective Visual Communication of Data, is the developer of the bullet graph and considered one of the leading experts in the use of data visualization for analyzing and presenting quantitative business information.
Let’s have a look at a Horizon Graph. Click to enlarge the screenshot of the chart:
What???? That’s my initial reaction and I bet it’s yours too.
Let us allow Stephen Few to explain what we are looking at. First some background:
This is not a marketing piece for Panopticon, so I’ll say little about the company except that until recently its products exclusively featured a particular visualization called a treemap. For information about treemaps, I invite you to read an article that their inventor, Ben Shneiderman of the University of Maryland, wrote for my newsletter back in April 2006 titled “Discovering BI Using Treemaps.” The folks at Panopticon applied the potential of treemaps in several innovative and practical ways, and are now complementing their products with the addition of several traditional graphical displays (for example, bar and line graphs), including a few new variations on these themes. One of these variations is called a horizon graph.
Steve is hard to impress and was intially skeptical about the Horizon Graph. Read about his two days with the Horizon Graph development team, however, and you’ll become interested also.
As for the example horizon chart shown above, here is what is going on.
I’ll begin with a quick explanation of the information that appears in the example above. It displays just under a year’s worth of daily changes in the prices (October 3, 2005 through September 29, 2006) of 50 stocks. The stocks are arranged by row, and time is displayed horizontally, from left to right. Rises and falls in stock prices relative to the price on October 3, 2005, the first day of the period, have been encoded in two ways: 2-D position—lines that move up and down as they proceed from left to right—and hue—increases in blue and decreases in red. Each of the graphs—one per stock—shares the same quantitative scale, so an increase or decrease of a particular distance for one stock equals the same degree of change as an increase or decrease of the same distance for another stock. In other words, the 50 graphs are an example of what Edward Tufte calls “small multiples”—a series of small graphs that are laid out within eye span for the purpose of comparison, which differ from one another only in that each represents a different set of values, in this case daily prices of individual stocks. By hovering with your mouse over any point along the timeline for one of the stocks, you can view the details regarding the selected stock at that point in time (stock name, price, and percentage change from the previous day) in a small window, as illustrated in the example.
Steve goes on:
This is the initial explanation that I received when I first examined Panopticon’s horizon graph. No more than a moment passed before I began expressing concerns, such as “Can a person really discern anything from this dense display that couldn’t be displayed more clearly and meaningfully?” I was doubtful, but unlike some development teams to whom I’ve posed such questions, the team at Panopticon had put a great deal of expert thought into the design of this visualization.
When Ben Shneiderman created the treemap, he was looking for a way to present a huge amount of quantitative information in a small amount of space (that is, a single screen). The results of this effort were bound to look a bit overwhelming to someone upon first sight, but because Shneiderman is an information visualization afficionado, people who take a few minutes to learn how it works can find the treemap quite useful.
Because Panopticon has focused primarily on treemaps, they’re familiar with the challenge of displaying a great deal of information in little space, so when they tackled the problem of simultaneously displaying a large number of time series, they had some useful experience to guide their effort.
Almost every good invention is developed in response to a particular problem. The horizon graph was developed in response to a need shared by many organizations:
to examine how a large number of items (stocks, product sales, employee satisfaction, and so on) changed through time
- to do so in a way that allows them to spot extraordinary behaviors and predominant patterns
- to view each of the items independently from the others when they wish
- to make comparisons between the items
- to view changes that occurred with enough precision to determine if further examination is required
In the stocks example, a single line graph with 50 lines would support some of the requirements to a limited degree, but most requirements, such as the ability to view each item in isolation from the others, would not be met. The data visualization challenge that Panopticon faced was formidable.
Please go to Steve’s newsletter Visual Business Intelligence to read the rest. There are explanations of enlarged charts such as this one:
Tags: Panopticon Horizon Graph, data visualization, horizon chart
PS. Of course it is natural to select graphic and charting tools to embed in our dashboards, but you may also want to further shortcut the development process by using an embedded dashboard. Think “OEM”. Meaning go with a dashboard vendor such as Klipfolio. Vendors whose core business is elsewhere in the business intelligence landscape may choose to embed dashboard software from a third party rather than develop it themselves.
Reminder: Please have a look at The Dashboard Spy List of Experts and see if you want to add a business intelligence resource to it.