The Horizon Graph

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:

Horizon Graph Example

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:

As Steve explains in his latest newsletter titled Time on the Horizon, the Horizon Graph was invented by the business intelligence software vendor Panopticon.

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:

Explaination of the horizon graph data visualization

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.

12 thoughts on “The Horizon Graph

  1. I wondered whether this would make an appearance.

    I’ve been mulling this over today and decided that this is probably a suitable graph for people with an IQ in the 140s and enough free time to work it out, but that many business users simply won’t be able to understand it, even if it is the most technically capable display medium for a particular business need.

    So I can see this being taken up by boffins, but it gets a very low rating in the usability stakes. Put another way, most graphs are about the data and the business problem. This one is about the intelligence and patience of the recipient.

    Personally I would only use it if all alternatives had been exhausted.

  2. lol. 140 IQ! ha ha. You crack me up, Mr. Tom.

    I must say I felt intimidated when I first saw that chart.

    The Dashboard Spy

  3. A couple of thoughts.

    1. Is the line graph needed? Could this not be a simpler visualization if the change each day is coded only in the intensity of red or blue – that is, the red or blue is the entire height of the line for each stock?

    2. If the stock were grouped by type (and a couple of options were given for sorting, such as sector, country, size, etc), then you could easily see multi-line blobs of red or blue that indicate that a group is moving in the same direction. Further, if a single stock is moving against the grain, that would add a lot of visibility.

    3. I’d love to know more about the use case for this graph. Who looks at 50 stocks over so many weeks on a single screen? What is her purpose in doing so?

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  5. OK so how about this? – what if you took out the area component and simply used colour hue for the whole thing? (Keep the flip between red and plue for the cross over between + and -)

    Have a continuous colour gradient rather than discrete steps and then each entry has a bar which is continually changing colour.

    It would be far less confusing.

  6. Disclaimer: I work for Panopticon but I’m not a dashboard designer or engineer.

    I can understand that it’s a bit hard to understand the real value of the Horizon Graph when looking at a static image. It really comes to life as an interactive visualization. It lets you filter out the less interesting info, group and re-group the data, zoom in, and there are hover displays that provide details on demand.

    I don’t think too many people will try to incorporate a Horizon Graph into a dashboard per se, but it’s a great thing to have on the screen when you need to compare charts for large numbers of entitities.

  7. Hugh – this horizon graph is fascinating. Is there a place on the web where we can see this in action? Better yet, is there a video of it where you guys explain it? It looks really interesting. Is it part of a BI software? How do I learn more?

  8. DataViz and mr tom:

    I’m working on a video and I’ll let you know when that’s available. There is some more info available on the Panopticon website.

    Of course we can easily show it to you in an online demo or something. Let me know if you’d like to do something like that.

    Horizon Graphs are part of our Visual Business Intelligence suite. They are available in the form of an SDK (Java or .NET) that you can use to embed the tools into your own app – or you can build your own VBI platform using the SDK.

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