Map Viewer allows you to explore your data in different ways through a variety of smart mapping styles. When you use Change Style in Map Viewer, the nature of your data determines the styling suggestions you see by default. Once you have decided how you want to present your layer, you can make changes to its appearance that are immediately reflected on the map. Map Viewer gives you control over styling elements such as color ramps, line weights, transparency, and symbols.
Sometimes you want to see how your data is distributed by category. Use the Types (Unique Symbols) style or the Types and Size style to do this.
Types (Unique symbols)
Use unique symbols to show different types of things (categorical data), not counts or numeric measurements. For example, you can use different colors to represent different rail lines in the city.
Note:
There is an absolute limit of 200 unique values, although only 10 colors are used, so the same color may represent multiple categories. This means that unique symbols works best with 2 to 10 categories of things—for example, restaurant types, tree species, and political parties.
To style your data by type using unique symbols, do the following:
- Follow the first four steps in the change style workflow.
- Choose an attribute to show.
- Click the Types (Unique symbols) style and click Options.
- Do any of the following:
- To change all the map symbols at once, click Symbols. For more information, see Change symbols.
- To customize any of the categories individually, click the colored symbol beside each category in the list. Depending on whether your data is points, lines, or areas, you will see appropriate styling options for each kind of symbol. For example, if your data is points, you can change the shape, fill color, stroke, and size of the point symbol.
- To reorder the categories, drag a category up or down in the list.
- Ideally, your layer should show fewer than 10 categories; more than 10 are difficult to distinguish by color alone. If you have more than 10 categories in your data, the 10 with the highest counts are shown, and those remaining are automatically grouped into the Others category. If the counts of your features can't be determined, the first 9 categories alphabetically are listed individually, and the rest are grouped in the Others category. To ungroup these observations one at a time, drag them out of the Others list and into the main list or click Move value out
. To ungroup all of these observations at the same time, click Ungroup 
. To hide features in Others, uncheck the box. To show them, keep the box checked. - To calculate and set the optimal visible range, click Suggest next to the Visible Range slider. You can also manually set the visible range by moving the slider.
- To change the transparency for the overall layer, move the Transparency slider to the left (less transparent) or the right (more transparent). To adjust the transparency applied to any individual category, click the color chip beside the category name. To adjust the transparency of unique locations per feature, click Attribute Values and choose an attribute field. You can only use this option if you have numeric data associated with your locations. For example, if your layer contains restaurant sales data, you can choose Type for the restaurants and set the transparency of the individual restaurants by their annual sales. If you want to hide the transparency ramp in the legend, uncheck the Show in legend box.
- Click OK when you are finished customizing your style or click Cancel to go back to the Change Style pane without saving any of your choices.
Types and Size
This style allows you to represent your data using different sizes and different categories by color. Choose a text or numeric field for unique values, and a numeric field for size values, and adjust each attribute's map symbol settings as needed. For example, use this style when you want to show a count attribute such as the number of people who have a graduate degree, and use a unique color for each value found in another field such as a county name.
To style two attributes using unique values and size, do the following:
- Follow the first four steps in the change style workflow.
- Choose the first attribute to show.
- Click Add attribute and choose the second attribute to show.
- Click the Types and Size style and click Options.
- Apply options to Unique symbols (first attribute) and Size (second attribute).