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More Value with Visualization

Weather Map ExampleChoropleth maps display quantitative data as a color, shading, or pattern and can show density, percent, average value or quantity of an event within a geographic area. Sequential colors on these maps represent increasing or decreasing positive or negative data values. Generally, each color represents a range of values with the most intense color being the highest and least intense color being the lowest. Choropleth maps can show the geographic distribution of a single variable, or the relationship between two or more variables. Data sets, such as population, ethnicity, income, language, political preference, annual rainfall, religion, etc, are easily visualized on a choropleth map. Analysis of data and presentation of data are common usages for these types of maps along with quick observation of patterns and variation.

Popular Use of Choropleth Maps:

  • Proposals
  • Research documentation
  • Marketing literature
  • Annual reports
  • Political Campaigns
  • Media
  • Health Trends
  • Crime Statistics
  • Census Data
  • Housing Trends
Example of Choropleth Map
Constructing a Choropleth Map
When creating a choropleth map, data is first put into classes or categories that are represented on the map by grades of color or shading. The greater the density of color or shading, the greater the density or value represented. In this map, counties are colored by age groups with the oldest age group being dark green and the lightest group being white. From the map, we can quickly see there is a large concentration of young people around Utah and northern Arizona. While such generalization may mask detail, it allows for quick observation of patterns and variation, and provides a basis for posing analytical questions.