using Topology and Node Value Differences
- example: compare national budgets across two years; what agencies disappear? which ones grow large absolutely? grow by large percentage? what other relationships
- put data in a tree, then encode absolute amount of change, color by percentage of change, outline based on removal and creation
- filter by layers in the tree, from top level departments, down to initiatives, down to accounts; quickly see where the changes have been made, what was created and what was eliminated
- synchronize across views for data painting/filtering and highlighting
- tested by letting participants try to perform comparisons without any training in the tool
- types of tree comparison: (type 0) topology but not node values; (type 1) values on leaf nodes only; (type 2) values on leaf and interior nodes; (type 3) type 1 + topology; (type 4) type 2 + topology; previous work has only done 0 and 1 successfully; this work focuses on type 2-4; only research known to address all these areas
- interesting analysis of actual 2012 and 2013 US federal budgets; another on airline passengers;
