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This documentation refers to the MongoDB Charts service in MongoDB Atlas. Read the on-premises documentation to learn how to use the MongoDB Charts on site.

Choropleth Chart

Choropleth charts are maps that use shading to depict differences across regions. The shading of a region (e.g. states, countries) is based on an aggregated value and is proportional to the corresponding value of other regions.

Unlike other geospatial charts, choropleths do not require coordinate data in your collections. Instead you can have names of regions as strings, so long as the region strings correspond to the names used in a supported Shape Scheme.

Regions

To help define regions, MongoDB Charts provides Shape Schemes. For example, with the US States scheme, you can define regions at a state level, and your location field value must be one of the 50 states.

Encoding Channels

Choropleth charts use the following encoding channels:

Encoding Channel Description
Location

Defines the regions to be shaded on the map.

The value must match (case insensitive) a region value for the selected Shape Scheme. For example, when using the US States scheme, the region of California matches california and CA as well as California.

For a complete list of shape schemes and their expected values, refer to the Shape Schemes page.

Color
Defines the Aggregation that determines the shading of the corresponding Location. You can customize the range of colors that corresponds to the relative aggregated values.

Use Cases

Choropleth charts can be used to depict differences in your selected aggregated field between geographic subregions, such as states or countries. They are useful when you have a dataset with clearly defined subregions compatible with one of the Shape Schemes MongoDB Charts provides.

A choropleth chart is a good choice to compare:

  • Population density across US states.
  • Annual rainfall across European countries.
  • Number of cellphone towers across Australian states.

See also

If you are looking for a chart to depict exact values rather than a high-level comparison, consider using a Data Table.

Example

The following choropleth chart visualizes the total count of movie releases across various countries. Each document in the collection contains an array of countries where a particular movie was released.

../../_images/choropleth-example.png

In this chart, we specify a Shape Scheme of World Countries to divide the map into countries.

The countries array in the Location field contains an array of elements representing each country where a movie was released. These elements match the values expected by the World Countries shape scheme. We unwind the array so each movie contributes to the count for each country where it was released.

The Color field of id is aggregated by Count. As a result, each country is shaded based on its number of movies released.

The custom color palatte for this chart ranges from yellow for lower ratings to dark red for higher ratings. Based on the visualization, we see that France, India, and Japan have relatively high movie release counts compared with other countries.

See also

For a complete list of choropleth Shape Schemes and their expected values, refer to the Choropleth Regions page.