Horizon Graphs for Code Churn

My advisor has asked that I do some posts as a journal for my software visualization work this semester. Some will hopefully come to fruition before the end of the semester. Do or die time, right?

The first idea that I’ve tweeted about, talked about, cannot shut up about is using a horizon graph to depict code churn. Currently, most of my work has centered around treemaps, but they have a weakness. They only depict one moment in time. Since code churn is concerned with the number of changes over time, a treemap will only show you code churn up to a certain moment in time.

This example horizon graph on Stephen Few’s blog shows the stock price performance for 50 stocks over 1 years. An increase in color saturation indicates an increase up or down. The hue indicates whether the change is positive (blue) or negative (red).

Although the example is from Panopticon, I’m confident that Processing could produce similar results. The idea is really genius, and says very good things about Panopticon. I starred this a while ago in reader. Recently, Alan Page turned me on to some papers by an expert at Microsoft, Dr. Nachi Nagappan. I’ve been rooting around in some of them and noticed that code churn is mentioned again and again. I also noticed that he’s frequently working with millions of lines of code. I don’t know how many components that adds up to, but I’d like to see if the horizon graph would still be useful with hundreds of components, or if it would overwhelm the viewer.

If we’re going for a t.h.u.d, I think you’d have the treemap for upper levels in a hierarchy of components. If the user wanted to investigate an area more there would be a click through to something like the horizon graph.

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