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    Treemaps display hierarchical data as a set of nested rectangles

    But there are no hierarchical data sets shown in this article! A list of countries is not hierarchical. A list of country / state / city would be hierarchical.

    Treemaps already have weaknesses, but for non-hierarchical data sets, they’re “pie chart junk”. Showing a single-dimensional quantity in two dimensions (an area) is almost always misleading.

    I’ve actually spent considerable time implementing TreeMaps. They’re a very finicky visualization to get right.

    But I recently learned / realized that “Flame Graphs” can take the place of treemaps:


    The name “flame graphs”, and even the look of them, doesn’t make you think they’re like treemaps. But the goal of both visualizations is to show you a weighted tree hierarchy, where the interior nodes have their own weights, not just leaf nodes.

    This is true for stack traces – a function can spend time in “itself” or it can spend time in the functions it calls. And the same is true for disk space – a directory can have space used by its immediate children, or in any of its descendants. In both cases you want to see this parent-child hierarchy.