Categorical Symbols for Vector Features
Included in this tutorial
Accessing the Categorical Symbology options, with point features
Employing categorical symbols based on one or more fields
Formatting categorical symbols, in the Symbol Format Gallery
Additional examples with polylines and polygons
Software version in examples: ArcGIS Pro 2.9.1
Tutorial Data: The tutorial includes demonstration with sample data available here.
Credits: L. Meisterlin (2022)
This tutorial walks through the steps of assigning symbols based on qualitative attributes or categories in a vector feature class’s attribute table.
The process for symbolizing vector features categorically is the same regardless of the geometry type. Still, this tutorial is symbolize three layers—points, lines, and polygons—from the Standard Data Package in Tutorial Data. It walks through the basic steps of accessing symbology options with a point feature class, then repeats those steps with demonstrations for the other layers.
Accessing the Categorical Symbology options (example: points)
Using the sample tutorial data, we will symbolize the point features in the Point1_Table1_join layer based on the values in the field called “Categ” (which is short for “Category”). This is a text (string) field with five different unique values.
the attribute field we will symbolize in this example
To access the symbology panel, right-click on the layer name in the Contents panel and choose Symbology. This will open the symbology panel if it is not already open. (In these demonstrations, left-clicks are represented in magenta and right-clicks are represented in yellow.)
In the symbology panel’s primary drop-down menu, we specify that we want to “Symbolize [our] layer by category” using “Unique Values.” This refers to unique values within the field(s) of the layer’s attribute table: each value will receive a different symbol.
HINT: The options within the Primary Symbology drop-down each include brief descriptions. Read through the others to learn more than these tutorials cover.
Once you’ve chosen “Unique Values” as the primary symbology type, the options within the panel will update.
First, choose the field with the attributes we want to symbolize via the Field1 drop-down. This dropdown includes a list of all fields within the layer’s attribute table. (Recall that numeric fields can also represent categories or qualitative variables.) In our example, we choose the Categ field.
As a result the values of the Categ field are listed, with default colors applied to each feature per value. The legend in Contents panel is also updated to reflect the contents of the Map view.
accessing the categorical (unique values) symbology options.
Additional fields
To symbolize features based on combinations of values from multiple fields, you can click the Add Field button.
Formatting Symbols
There are two ways to change the symbols’ format.
First, you can choose a pre-set color scheme from the Color Scheme drop-down.
Alternatively, you can access the Format Properties per symbol by double-clicking on each swatch in the symbol list. This will summon the same options available for the single-symbol formatting, covered in Single Symbols for Vector Features.
The demonstration below shows accessing both of these formatting options.
accessing symbol format options
Additional Options
In the demonstration below, we walk through a few more useful options.
Notice that the icons at the top of the symbols list include options for adding all values (if your list of unique attributes is too long to load all values automatically) as well as adding specific unlisted values (if you want to symbolize certain attribute values but not others).
The More drop-down menu includes an option to show the count per symbol. This is the number of features per value as symbolized.
This drop-down also includes formatting options to apply to all symbols (rather than adjusting format properties per symbol, one at a time, as shown above).
The Label column of the symbol list is editable: You can change the way values are labeled within your legend, for example. (In the demonstration below, we capitalize the labels per value.) Notice that the legend list in the Contents panel updates with each change. This would also update values in a legend within a Layout.
You can also change the listing order of the symbols using the “move” icon buttons. (In the demonstration below, we reorder the categories by moving the Gamma values from the bottom of the list to third.)
Lastly, for good measure, we manually edit the “Categ” label in the contents panel.
Additional options: the More drop-down, relabeling category values, reordering symbols.
For good measure (because it is cropped out of the demonstration gif above), at right is a screenshot of the full contents of the “More” drop-down menu.
Review & More (example: polylines and polygons)
In the demonstration below, we apply a categorical symbology to the subway lines (based on the colors commonly used to represent the routes) and to the Tracts_wTable polygon layer based on the “Type_AB” field.
For the subway lines:
Choose individual color symbols per value in the rt_symbol field. (This attribute field is made for this purpose.)
Specify the order in which the features should be drawn (from top to bottom) by enabling Symbol Order Drawing.
Change the thickness of each line feature by formatting all symbols.
For the tract polygons:
Assign symbol colors based on a pre-set color scheme.
Change the line/stroke color for all polygons by formatting all symbols.
review with lines and polygons