Choropleth interactive maps

In an Interactive Map visual, CDP Data Visualization enables you to create choropleth maps. A choropleth map shows geographical areas that are shaded in proportion to the value of the measurement that is displayed on the map.

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Consider the following when building choropleth maps:

Use choropleth maps when your data is attached to enumeration units, such as counties, countries or zip codes.
Standardize data to show rates and ratios instead of raw data counts. For example, instead of plotting gross GDP, plot GDP per capita.
Use choropleth maps when you have data with continuous statistical surface. For example, Population is a count and representing it in colored map may be misleading. Population density is a ratio with a continuous statistical surface (even where 0 represents unpopulated areas); so it can be used in choropleth maps.

In this example, you will create a choropleth map that colors the average tax liability in California by zip code. The choropleth Interactive Map visual is based on the Personal Income Tax Statistics by Zip Code dataset. For an overview of shelves that specify this visual, see Shelves for interactive maps.

To create a choropleth map, you must specify the following for each visual:

Custom mapbox style, which has a choropleth shape file in it. For more information, see Adding a custom mapbox style.
Layer ID, which is the name of a unique layer within the Custom Mapbox style that identifies the shapes that you would like to color by a measure in your data. For more information, see Specifying a choropleth layeer ID.
Geo-type as Shape ID: The dataset must have at least one field in the Geo shelf to determine the location on the map. You must change the Geo-type to Shape ID. A Shape ID is a key that joins the shapes in the Custom mapbox style and the field in the Data Visualization dataset. This helps in identifying the measure that maps to the shape. This Geo field must be in the dataset that was used to create the custom mapbox style.

Start a new visual based on the National Geographic Features dataset.
For instructions, see Creating a visual.
In the VISUALS menu, find and click Interactive Map.

The shelves of the visual changed. They are now Geo, Measure, Colors, Tooltips, and Filters. The only mandatory shelf for map visuals is Geo.
Populate the shelves from the available fields in Dimensions and Measures in the DATA menu.

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To create a choropleth map, the dataset must have at least one field in the Geo shelf with Geo-type Shape ID.
1. Select the zip_code field and drag it to the Geo shelf to identify the shapes by zip code.
2. Cast this to the appropriate Geo Type: click the field on the shelf, and in the Field Properties menu, select Change Type, and select Shape ID. This helps in identifying the measure that maps to the shape.
3. Under Measures, select the avg(total_tax_liability) field, and drag it to the Colors shelf.
4. Change the aggregation from total_tax_liability, by selecting Aggregates Average
  This colors the average tax liability in California by zip code.
Navigate to the Map Style menu under Settings, and enter a Custom mapbox style that you have obtained from Mapbox. Make sure that this style has a choropleth shape file in it.
Navigate to the Choropleth menu under Settings, and enter a Layer ID.
Choropleth Layer ID identifies the shapes that you would like to color by a measure in your data.
Click REFRESH VISUAL.

The choropleth map visual appears.
If the visual does not display a choropleth map, check that the Geo-type of the zip_code field is set to Shape ID.

Proceed to Customizing the choropleth map.