I’ve been meaning to get back to TreeMaps for awhile. The recently unveiled Many-Eyes includes a TreeMap visualization. Martin Wattenberg (who did some research on TreeMap layouts) provides a typical example:

My main complaint with TreeMaps is their ugliness. Every TreeMap I have seen, including this one, look disorganized. Basically, we can only see the top level of the hierarchy, indicated with the strong dark lines and labeled. All other levels disappear into the patchwork mess. So one of the “strengths” of TreeMaps, the ability to directly view the hierarchy, is effectively neutered.

The layout also ignores good graphic design. Elements are not aligned and they do not visually cluster in meaningful ways. This is in contrast to indented lists, another common way to show hierarchical data, which use alignment and clustering very effectively to communicate the organization of the hierarchy.

More effective use of whitespace could dramatically improve the appearance of TreeMaps, but so few people use it well. Here‘s an example that does. Also notice how the alignment makes the diagram look very organized.

Next time: the travesty of Cushion TreeMaps.

Category: visualization One comment »

One Response to “TreeMaps”

  1. James Fogarty

    Might be worth a peek at what Hao Lu did with cascaded treemaps.

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