Retention Flow Tables and Sankey Diagrams // Creates transition tables, summaries, and interactive Sankey diagrams from longitudinal person-term-state data. Sankey diagrams visualize flows between states with link widths proportional to flow counts; see Kennedy and Sankey (1898) "The Thermal Efficiency of Steam Engines" doi:10.1680/imotp.1898.19100 and Schmidt (2008) "The Sankey Diagram in Energy and Material Flow Management: Part I: History" doi:10.1111/j.1530-9290.2008.00004.x. The minimum input schema is one row per person per term with an identifier, term, and categorical state.