ChoroWare: A Software Toolkit for Choropleth Map Classification

Choropleth mapping plays an important role in exploratory spatial data analysis. Several objectives have been suggested to guide choropleth map construction. These objectives, however, often conflict and, consequently, a choropleth map that is best for one objective may not be best for others. Choosing a set of choropleth class intervals is thus a multiobjective problem. This article describes an open-source software toolkit, called ChoroWare that is designed to help cartographers identify class intervals that are suitable for a specific application. The software uses a genetic algorithm to generate a set of nondominated solutions to the multiobjective choropleth class interval problem and uses an interactive visualization tool to display members of this classification set. Using ChoroWare, cartographers can examine trade-offs between alternatives and find desirable choropleth classifications that meet their objectives.