Sean blogged the other day about using a treemap to visualize the drivers of the Australian Inflation. He got inspired to create a treemap by an NYT article that used an interactive version of the following treemap:
This chart looks nice on the first view. It makes nice use of muted colors, the shapes look well balanced and certainly the graphic designer did a good job. However, from a data visualization perspective this chart has a couple of flaws.
Treemaps: A Visual Breakthrough for Monitoring Complex Activities
Ben Shneiderman designed Treemaps to visualize deep directory tree structures.
Ben explained treemaps in an article as:
“Among the growing family of visual analytic tools, treemap are flourishing in organizations that require daily monitoring of complex activities with thousands of products, projects, or salespeople. Tabular reports, bar charts, line graphs, and scattergrams are important tools, but for complex activities where there are numerous sales regions, manufacturing plants, or product lines the hierarchical structures provided by treemaps can be helpful. While tabular displays and spreadsheets can show 30-60 rows at a time on typical displays, the colorful presentations in treemaps can accommodate hundreds or thousands of items in a meaningfully organized display that allows patterns and exceptions to be spotted in seconds.[…] Treemaps are a space-filling approach to showing hierarchies in which the rectangular screen space is divided into regions, and then each region is divided again for each level in the hierarchy.”
The Limitations of Asymmetric Shapes in Treemap Design
The first problem the NYT chart has is that it does not visualize the hierarchy as rectangular areas. The inflation drivers are visualized as asymmetric round shapes. It is difficult to compare the relative size of rectangular shapes but it gets almost impossible for asymmetric shapes. Also does this treemap lack labels for the smaller inflation drivers.
A Treemap Reimagined: Solutions to Visualization Challenges
Sean published in his blog post a treemap which does not have the problems mentioned above:
Ben designed treemaps to visualize thousands of regions, products, etc ; but the Inflation chart only comprises 20 Inflation Drivers grouped into 7 categories. A simple sorted table would do a better job communicating the numbers as Kaiser Fung from Junk Junks wrote in his post.
A Sparkline Solution: Graphic Table Enhances Data Clarity
Inspired by this post and Sean came up with this graphical sparkline table designed with Excel and MicroCharts.
This is already quite an improvement on the treemap, as we can see increasing and decreasing inflation trends and sparklines rather than traffic light colors as in the tree map version. Also it is much easier to read for non expert users.
Minor Improvement Suggestions
Some minor things we can improve in Sean’s chart are:
- We can sort the inflation drivers by Weight, to have the most important ones at the top
- Changing the area to the sparkline puts emphasis on the trend rather than the absolute value of the values (as the area chart does)
- Inline deviation charts allow us to visualize the MoM and YoY % changes
