Pie chart symbols are used in maps to show the proportions of categorical data associated with a single feature, using either a count or a summary statistic. Pie chart symbols are created on a map using a string field and a location field containing coincident values.
Pie chart symbols can answer questions about data, such as the following:
- What are the proportions of categories for each feature?
- What is the count or summary statistic relative to another location?
An insurance company is reviewing purchases of its policies across the United States to determine where there is market potential for each policy class (automobile, disability, life, and property). The analyst in charge of the review joins the insurance portfolio data for the company with a state boundary layer and uses the result to create pie chart symbols showing the proportions of each policy class that are being purchased in each state, with each pie chart sized by the number of policies in the state.
The analyst can use associated charts, filters, or the map legend to determine which states have potential for each policy class. The analyst selects automobile policies and sees that there is low automobile insurance uptake across the Midwest. The analyst will do more research to determine why there are states with low or no automobile insurance uptake (for example, is automobile insurance not offered, or is there a major regional competitor?) and whether there is potential to increase uptake in those states.
Create pie chart symbols on a map
Pie chart symbols can only be created with multipart datasets in which features are collocated. These datasets can be created using a one-to-many join, or by enabling location on a dataset. If location is enabled with addresses or coordinates, Repeat identical features must remain unselected.
Complete the following steps to create a map with pie chart symbols:
- Create a multipart dataset using one of the following methods:
Create a join between two datasets. Generally, these datasets will include the features you want to display as pie chart symbols and a boundary layer.
The join should be one-to-many, meaning each boundary feature contains more than one feature to create the pie chart. In the example above, a join was created between a dataset with insurance data and state boundaries.
Enable location for your dataset.
If you enable location for points using addresses or coordinates, Repeat identical features must remain unselected. This method should only be used in situations where multiple data points appear in the exact same location. For example, a dataset containing monthly status updates for fire hydrants in a city could contain a new input each month for each fire hydrant. Enabling location without repeating identical features will aggregate the inputs for each hydrant.
If you enable location using geography, there should be multiple features within each boundary. This method functions the same as a one-to-many join.
- Expand a dataset in the data pane so that the fields are visible.
- Select one of the following combinations of fields:
- A location field plus a string field
- A location field, a string field, and a number or rate/ratio field
If you created a join in step 1, the location field you select must be the field that corresponds to the boundaries.
You can search for fields using the search bar in the data pane.
- Drag the fields to the page and drop them on the Map drop zone.
A map is created.
If the map was created using a location field, string field, and number or rate/ratio field, then the map will be styled using pie chart symbols. If the map was created using a location field and a string field, then the map will be styled using unique symbols. Complete the following steps to change the unique values to pie chart symbols:
- Expand the legend to display the Layer options pane.
- Browse to the Symbology tab .
- Change Symbol type to Pies.
The Layer options pane is accessible by clicking the arrow next to the layer name and includes the following configuration options:
- Use the Legend tab to view the unique values on the map and make selections based on the values. To change the color associated with a value, click the symbol and choose a color from the palette or enter a hex value.
- Use the Symbology tab to do the following:
- Change the field and statistic displayed on the map or switch to a different type of map.
- Change the classification type and number of classes.
- Use the Annotation tab to configure the map pop-ups for the layer.
- Use the Appearance tab to do the following:
- Symbols—Change the symbol style properties, such as symbol size, outline style, and layer transparency.
- Layer effects—Enable bloom and drop shadow effects.
- Use the Attributes tab to view details for features that are selected on the map.
Use the Visualization type button to switch directly between a map with pie chart symbols and other visualizations, such as a summary table, stacked bar chart, chord diagram, or treemap.
Click the Flip card button to turn the map card over. The back of the card includes a count of features and a text box for a description of the map.
Pie chart symbols show all unique categories associated with a single feature or location. If the features contain many unique categories, the pie chart symbols may be difficult to interpret.
Use the following resources to learn more: