Map Viewer allows you to explore data in various ways through a variety of smart mapping styles. When you style map layers in Map Viewer, the nature of the data determines the default styling options. You can experiment with color ramps, line weights, transparency, symbols, and other graphic elements, and see your choices reflected immediately on the map.
To distribute data by category, use the Types (unique symbols) style or the Types and Size style.
Types (unique symbols)
Use unique symbols to show various types of categorical data, not counts or numeric measurements. For example, you can use different colors to represent wind turbines by manufacturer.
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 work best with 2 to 10 categories of data—for example, restaurant types, tree species, and political parties.
To style data by type using unique symbols, do the following:
- Follow the first five steps of Apply a style.
- In the Styles pane, click the Types (unique symbols) style if necessary and click Style options.
Tip:
To show time-based categories on the map, use the Discrete Time Periods (categories) style.
- Optionally, do any of the following:
- Click a symbol under Symbol style to change all the map symbols at once, and specify the symbol options. For more information, see Use style options.
- Turn on the Display features by value order toggle button to set the display order of overlapping features on the map based on the order of categories shown in the Style options pane and legend. If you turn on this option, overlapping features in categories that are higher in the list are drawn on top of features in categories that are lower in the list.
- Click the colored symbol next to each category in the list to customize any of the categories individually. Depending on whether the data consists of points, lines, or areas, applicable styling options are shown for each type of symbol. For example, if the data consists of points, you can change the symbol shape, fill color, and outline.
- Drag a category up or down in the list to reorder the categories in the legend individually. To reorder multiple categories, check the box next to each category and click Move up or Move down to change their position in the group. This order also affects the feature display order if you turned on the Display features by value order toggle button.
- Group the categories into subcategories to add detail or context to the map legend.
- Include fewer than 10 categories in a layer for best visualization; more than 10 are difficult to distinguish by color alone. If you include more than 10, only the 10 with the highest counts are shown. The remaining are automatically grouped into the Other category. If the counts of the features can't be determined, the first 9 categories are listed individually in alphabetical order, and the rest are grouped in the Other category. To move one or more observations out of the Other list and into a main group, check the box next to each category, click Move to group, and select the group to which the observation will be moved. To hide features in the Other category, uncheck the box. To show them, leave the box checked.
- Click Options
next to the group name and do any of the following: - Click Add value to add a new value to the group.
- Click Change group colors to change the group color ramp.
- Click Select all values to select all values in the group. Click Clear selection to clear the category selection.
- Click Move up or Move down to reorder the group in the group list.
- Click the color chip next to the category name to adjust the transparency applied to an individual category. Click Transparency by attribute to adjust the transparency of unique locations per feature, and specify the transparency settings. You can only use this option if you have numeric data associated with the locations. For example, if the layer contains restaurant sales data, you can style the data according to the type of restaurant and adjust the transparency of each category proportional to its annual sales.
- Manually add a category for values that do not yet exist in the data.
- Merge multiple categories into one category represented by a single symbol.
- You can rotate symbols based on a numeric attribute if you are mapping point symbols. For example, the color of the points can depict air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Group the categories
When styling a layer to show categorical data, you can organize the categories into groups to add detail or context to the map legend. For example, if the map shows crimes by type—arson, assault, theft, burglary, and so on—you can organize the crime categories into groups such as violent crimes and nonviolent crimes.
To create category groups, do the following:
- Check the box next to the category or categories you want to select and click New group.
A new group is created with the category in it. The category list and legend update to show two groups.
- Click the temporary title for the new group, type a new title, and press Enter.
- Repeat the previous step to give the other group a title.
- Drag other categories into the new group, or check the box next to each category to select multiple categories, and click Move to group.
- Repeat the previous steps to create additional groups.
- To revert the category list to a single group or remove groups, drag each category out of the group you want to remove. Alternatively, check the box next to each category to select and move multiple categories.
Manually add a category
The Types (unique symbols) style creates categories based on existing values in the data. However, you can also manually add categories for values that do not yet exist in the data. Then, when a field in the data is updated to match the value you specify, the styling for that feature automatically updates.
To manually add a category, do the following:
- Follow the first two steps of the section above to style the layer using Types (unique symbols).
- Click Options next to the group name and click Add value.
The Add value pane appears.
- Type a stored value in the Value text box.
Locations with a value for the selected field that matches the stored value appear in the new category.
Note:
Stored values must be unique. Values for manually entered categories cannot match existing values in the data or values for other manually added categories. - Optionally, if you want the category name to be different than the stored value, type a displayed value in the Label text box.
- Click Done.
The new category is added and appears in the category list.
- To delete a manually added category, drag it into the Other category. To delete multiple manually added categories at the same time, check the box next to each category, click Move to group, and choose Other.
Merge the categories
When styling a layer to show categorical data, you can merge two or more unique categories into a single category. This shortens the map legend and allows you to apply the same styling to all values that have been merged into one category. For example, if the map shows crimes by type—arson, assault, theft, burglary, and so on—you can merge the crime categories into two groups: violent crimes and nonviolent crimes.
To merge categories, do the following:
- Check the box next to the categories you want to merge and click Merge values.
The selected categories are merged into a single category shown as a comma-separated string. The category list and legend update to show a single category.
- To merge additional categories, check the box next to the merged category, select additional categories, and click Merge values.
- To revert a merged category to individual categories, check the box next to the merged category and click Separate values.
The merged category is separated into individual categories. The category list and legend update to show multiple categories.
Note:
You can merge categories from the same group or from different groups. Categories are merged with the value that has the highest position in the display order. When separated, categories remain in the group into which they were merged and appear as individual values in that group.
Types and Size
This style allows you to represent the data using different sizes and 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, in a map about unemployment in the United States, you can use this style to show a count attribute, such as the number of unemployed people per county, and use a unique color for each value found in another field, such as the state.
To style two attributes using unique values and size, do the following:
- Follow the first five steps of Apply a style.
- Choose a second attribute field or expression.
- Click the Types and Size style and click Style options.
- Choose and apply options to Types (unique symbols) (first attribute) and Counts and Amounts (size) (second attribute).
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.