Nominal Area Choropleth Maps

http://www.veiled-chameleon.com/weblog/archives/2004_07.html

Nominal area choropleth maps are used to represent nominal data on a map so that it may be understood easier. For instance, this map represents the different swing states during the 2004 Presidential Election. This deals with nominal data because each state gets a color that is based off of its political majority of people.