Guerra Gomez, J., Buck-Coleman, A., Plaisant, C., Shneiderman, B. (October 2011)
A common data analysis task is to compare pairs of trees to detect changes in leaf or interior node values and to identify created and removed nodes. However even in trees with just a dozen nodes it is difficult to find those differences. We present TreeVersity, a new interactive visualization that gives users powerful tools to detect both node value changes and topological differences. TreeVersity uses dual comparison techniques (side-by-side and explicit differences) and tabular representations, to facilitate the understanding and navigation of the differences. TreeVersity's design employs carefullydesigned color palettes to show positive/negative, absolute, and relative value changes; shapes that preattentively show these changes; and novel graphical approaches that highlight created and removed nodes. We illustrate TreeVersity's functionality through comparison of the 2011 and 2012 U.S. Federal Budget. Eight usability test participants, with no initial training, identified many differences between the two trees, while suggesting improvements which were implemented.