Choropleth Map

Choropleth maps are a type of heatmap that visualizes geographical areas or regions, shaded in proportion to their aggregated values. Darker, more intense colors typically represent larger data values. Choropleth maps are best suited for showing how a measurement varies across geographical regions — for example, ranges of income across different zip codes, or the number of organ donors across different countries. To create a choropleth map, you must select the region for analysis. Choropleth maps support all countries, as well as US states and cities.

Required Columns

Choropleth maps use one geolocation column to determine regions on the map, and a value column to be measured in those locations. Before you can create a Map Chart, your data needs to be prepared for the correct use of maps, which is done by adding a Geolocation Group to your data.

Each Map Chart needs at least one geolocation group to identify the parts of an address that will be used for positioning locations on the map. This can be set in the Design section of Datasets. Define these groups correctly for accurate map locations.

Use Case

The type of analysis that can be best performed with a choropleth map usually involves the variations of a measure over its range and geographical regions. The questions that lead to choosing a choropleth map for visualization are “How does each [geolocation] fare against others in terms of [measure]?” or “In which range of [measure] does each [geolocations] fall?” Examples of this type of analysis include:

• “How does the average amount of rainfall in each state compare to each other?” Or “Which states get more rainfall than others?”
• “Where, in the range of far left to far right, does each zip code’s voting statistics fall?”

Note: The question is never “how many”, or “how much”. To display numbers that answer such questions, use a Bubble Map.

Create a Choropleth Map

To create a choropleth map, drag and drop a data field from a geolocation group into the Geolocation shelf and a measure as the Values field. The data in the selected measure will be divided into 5 equal ranges by default and each range associated with a color from the color sequence of the selected theme. Each region of the selected geolocation column is colored according to where it falls in the range of the selected measure.

The following use case compares sales in US cities.

1. Drag and drop country as Geolocation and quantity as Values.
2. Go to the General section to add Total Price to the Tooltip and choose Currency as the Values Format.
3. In the Styles section, set the Theme that matches your visualization needs. For heatmaps, consider using a theme with a gradient.

Style the Choropleth Map

In the Configuration Panel on the right of the Chart Builder, you can style different aspects of your map.

General

The General section is available for all chart types, and the options vary depending on the chart selected.

Styles

The Styles section enables you to control various visual elements of the charts, such as colors, labels, and more. It is available for most chart types, and the options vary depending on the chart selected. Style options specific to this chart include the following:

• Theme - Set one of the predetermined themes for shading your regions. In most cases, it makes sense to use a gradient spectrum for a choropleth map.
• Map Region - Select a predetermined areas as the initial view of the map. You can zoom in or out of the selected area.
• Map Borders - Show or hide country and region borders on your map.
• Custom Scale - By default, the choropleth map divides the range of data, from the smallest value to the largest, into 5 equal buckets and assigns each one color from a spectrum of five. You can change which range of data to depict in the heatmap by selecging the lower and upper limit. Decide how many buckets to break the range into by selecting the Color Steps:
  • Color Steps - Number of different colors used in the chart.
  • Min Range - Set the minimum of the Values data field.
  • Max Range - Set the maximum of the Values data field.
• Reversed Colors - Reverse the sequence of the colors applied from the theme.
• Data Labels - Show or hide value labels of your data points.

Format

You can apply Conditional Formatting to Choropleth Maps.

Filters

You can add filters to your data by expanding the Filters section in the configuration panel or selecting Filters in the toolbar above the canvas. Filters that are created in the Chart Builder are hidden from end users. You cannot edit or interact with these filters in view mode.

For more information, see Map Chart.