3 Charts You Should Be Using, But Aren't
The data design explosion of the last few years has led to countless new solutions for displaying and comparing data visually. And yet, in presentations, most people fall back on the old standards: pie, bar and line charts. Often, simplicity is the best route and a good bar chart is the best solution. But there are other simple, yet little-used charts that you might consider adding to your presentation toolbelt. Here are three that I use all the time in place of those pie, bar and line charts.
Area Circles
A traditional bubble chart plots differently sized circles on an x-y axis, allowing for 3 simultaneous scales. (Take a look at how Hans Rosling uses and animates bubble charts.) But most often with presentation, I don't need the x-y scale and just want to visually compare a set of numbers, so I get rid of the underlying grid and use the sized bubbles, or what I call area circles. A couple of examples...
How do you create accurate area circles? One way is to use Microsoft's native bubble chart function. Enter your data points for the size of the circle (ignore the x-y values) and produce a bubble chart. Then create simple PowerPoint circles on top of the chart that match the sizes of the chart's bubbles. You now have accurately sized area circles that you can collectively size up and down as needed by your layout. (Then you can delete the actual bubble chart.)
Another method for creating accurately sized area circles is make each by scratch using math. As much as I hate math, this is actually how I usually go about it. As you might remember from school, Area = Pi x r2. Take the value of the metric—for example, "10"—and plug it into an area of circle calculator (like this one.) Take the resulting radius figure—"1.78"—and double it to determine the size of the circle you should create in PowerPoint. In this case, you'll create a circle 3.56" big. It sounds a bit involved, but once you get going with it, it's actually quite simple.
Tree Maps
Think of a tree map as a cross between a bubble chart and a stacked bar chart. Here's one I used to compare past year client growth. In this case, specific numbers were not important—just the overall visual story. And by using a tree map, I was able to make better use of logos than I would have with a pie or bar chart.
To create a tree map, you're going to want to use special data visualization software. I use the tools as ManyEyes.com which is a free and experimental site from IBM which can make unique visualizations for you in with just a few clicks. For tree maps, I paste my data from Excel into the site, select "Tree Map" and voila, my visualization is created for me as an image. I then take the image into PowerPoint, and recreate the tree map with PowerPoint shapes, "tracing" the squares.
David McCandless uses tree maps to great effect, like with his "Billion Dollar-O-Gram" visualization below. Check out more of his work at his site.
Bullet Graphs
Often data points need to be presented in comparison not just to other data points, but to previously established or future goals or targets. In cases like these, I use a form of bar chart called a bullet graph, invented by Stephen Few. Created originally for data dashboards as a more effective alternative to gauges and thermometers, a bullet graph simply shows progress towards a target or targets. Here's an example of data in need of a bullet graph.
The presenter here had cleverly created an overlapping bar chart with the 5-year and long-term targets as bars that he turned into dotted boundary boxes. But the problem was that these targets were difficult to decipher from the legend. Furthermore, at first glance I assumed that the colored shadings were actually the targets and not the progress since generally targets are larger than the progress. But in this case, the progress has far exceeded the targets for "Land" and for "Water." "Energy" is almost at target. To address the confusion, I turned the chart into a bullet graph and direct labeled the two targets on the top bar only. Then, by bringing the colored progress bars to the forefront and letting the targets recede into the backround of this chart as shades of gray, the overwhelming success story of these numbers becomes crystal clear.
You can read more about bullet graphs in Stephen's excellent book, Information Dashboard Design and at his blog, Perceptual Edge.
