Method Overview

Method Details

createRenderer(params){Promise<RendererResult>}

Generates a DotDensityRenderer based on one or more complementary numeric fields and/or Arcade expressions. This method will determine an appropriate dotValue for the data at the scale of the provided view.

For example, suppose you have a layer of U.S. counties with fields containing the total sales of various crops: wheat, soybeans, corn, cotton, and vegetables. If a feature has the following values for each field:

Field Name	Count	Color
Wheat	140	purple
Soybeans	2000	blue
Corn	0	yellow
Cotton	300	green
Vegetables	120	red

This method will generate a renderer that may determine the dotValue should be 20. The feature with the data above will be rendered with a random placement of 6 purple dots, 100 blue dots, no yellow dots, 60 green dots, and 5 red dots.

The suggested value is calculated based on a sampling of features. So executing this method multiple times using the same parameters may yield varied results.

Other options are provided for convenience for more involved custom visualization authoring applications.

Parameters:

Specification:

params Object Input parameters for generating a dot density visualization based on a set of complementary numeric field(s). See the table below for details of each parameter. Specification: layer FeatureLayer|GeoJSONLayer The polygon layer for which the visualization is generated. view MapView The MapView instance in which the visualization will be rendered. attributes Object[] A set of complementary numeric fields/expressions used as the basis of the dot density visualization. For example, if creating an election map, you would indicate the names of each field representing the candidate or political party where total votes are stored. Specification: field String optional The name of a numeric field. label String optional The label describing the field name (or category) in the legend. This is should be used if the given field doesn't have an intuitive field name or alias. For example, for a field named dem representing the total vote count for the Democratic party, you can set the label to Democrat to clarify the name of the category in the final visualization. valueExpression String optional An Arcade expression that returns a number. This expression can reference field values using the $feature global variable. This property overrides the field property and therefore is used instead of an input field value. valueExpressionTitle String optional Text describing the value returned from the valueExpression. basemap String|Basemap Deprecated since version 4.13. Use view instead. optional Default Value: gray The named string or basemap object of the Esri basemap that will be paired with the output visualization. Determines optimal colors for the output renderer. dotValueOptimizationEnabled Boolean optional Default Value: true Indicates whether to vary the value of each dot by the view's scale. This will set the referenceScale of the output renderer. dotBlendingEnabled Boolean optional Default Value: true Indicates whether to enable color blending of different colored dots rendered at the same pixel. This is only visible in highly dense and highly diverse features. outlineOptimizationEnabled Boolean optional Default Value: false Indicates whether the polygon outline width should vary based on view scale. When false, no outline will be used in the output renderer. legendOptions Object optional Provides options for modifying Legend properties describing the visualization. Specification: unit String optional Indicates the unit represented by each dot in the legend. For example, in a population density map, you might set the value of people to this param. The output renderer would display 1 dot = 300 people in the Legend. dotDensityScheme DotDensityScheme optional In authoring apps, the user may select a pre-defined dot density scheme. Pass the scheme object to this property to avoid getting one based on the basemap.

Returns:

Type	Description
Promise<RendererResult>	Resolves to an instance of RendererResult.

Example:

const layer = new FeatureLayer({
  url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/ArcGIS/rest/services/USA_County_Crops_2007/FeatureServer/0"
});

// will create a visualization of predominant crop by U.S. county

const params = {
  layer: layer,
  view: view,
  attributes: [{
    field: "M217_07",
    label: "Vegetables"
  }, {
    field: "M188_07",
    label: "Cotton"
  }, {
    field: "M172_07",
    label: "Wheat"
  }, {
    field: "M193_07",
    label: "Soybeans"
  }, {
    field: "M163_07",
    label: "Corn"
  }]
};

// when the promise resolves, apply the renderer to the layer
dotDensityRendererCreator.createRenderer(params)
  .then(function(response){
    layer.renderer = response.renderer;
  });

Type Definitions

RendererResult

The result object of the createRenderer() method. See the table below for details of each property.

Properties:

renderer DotDensityRenderer The object representing the dot density visualization. Set this on a layer's renderer property to update its visualization.

dotDensityScheme DotDensityScheme The dot density scheme used by the renderer based on the given basemap.

basemapId String The ID of the basemap used to determine the optimal colors of the dots.

basemapTheme String Indicates whether the average color of the input view's basemap is light or dark.