Renderers define how to visually represent each feature in one of the following layer types:

• FeatureLayer
• SceneLayer
• MapImageLayer
• CSVLayer
• StreamLayer

The Renderer object contains drawing information for the layer and is the base class for all renderers.

There are several types of renderers available for visualizing data. Each serves a different purpose, allowing you to explore your data and tell a visual story about it by combining geography and statistics. Most cartographic visualizations fall into one of the following categories.

Location

In many cases, the user just wants to see where a set of features are located. Some examples might be political boundaries, cities, buildings, rivers, etc. These are scenarios where you want all features in the layer to have the same symbol. To accomplish this you would use a SimpleRenderer.

The example in the screenshot below contains three layers; each uses a SimpleRenderer to assign all features the same symbol. The polygon layer represents states with no fill and a gray outline. The polyline layer visualizes highways with bright blue lines. The point layer depicts cities as marker symbols with the same bright blue color.

Read more on the SimpleRenderer page.

Unique types

UniqueValueRenderer allows you to symbolize features based on one or more matching string attribute values. Unique values are typically differentiated with colors, fill styles, or images to represent features of various types.

In the image below, each line is symbolized with a different color depending on the jurisdiction to which the highway belongs. For example, green lines are highways in the "Tampa District" whereas red lines are highways in the "Central District".

Read more on the UniqueValueRenderer page.

Class breaks

ClassBreaksRenderer sets the symbol of each feature in a layer based on the value of a numeric attribute. Symbols are assigned to classes, or ranges of data. Each feature is assigned a symbol based on the class in which the value of the attribute falls. In the example below, a FeatureLayer representing block groups is rendered with a ClassBreaksRenderer. Features where fewer than 35% of the population have a college degree are rendered with a deep green color. Features where between 35% and 50% of the population have a college degree are rendered with a pale green symbol. The other features are similarly rendered based on the value of the attribute of interest.

Read more on the ClassBreaksRenderer page.

Continuous ramps and multivariate visualizations

Rather than manually creating several class breaks to visualize numeric data, you can depict more variation in your layer using continuous styles. The color, size, opacity, and rotation visualVariables allow you to do this in either a SimpleRenderer, UniqueValueRenderer, or ClassBreaksRenderer.

The example below uses a UniqueValueRenderer with an opacity visual variable to map predominant types and the strength of their predominance in relation to other variables.

See visual variables for more information.