ESM: import HeatmapRenderer from "@arcgis/core/renderers/HeatmapRenderer.js";
CDN: const HeatmapRenderer = await $arcgis.import("@arcgis/core/renderers/HeatmapRenderer.js");
Class: @arcgis/core/renderers/HeatmapRenderer
Since: ArcGIS Maps SDK for JavaScript 4.8
The HeatmapRenderer uses kernel density to render point features in FeatureLayers, CSVLayers, GeoJSONLayers and OGCFeatureLayers as a raster surface.
To create this visual, the HeatmapRenderer fits a smoothly curved surface over each point. The surface value is highest at the location of the point and decreases proportionally to the distance from the point, reaching zero at the distance from the point specified in radius. The value of the surface equals the field value for the point, or 1 if no field is provided. The density at each pixel is calculated by adding the values of all the kernel surfaces where they overlay.
Because there isn't an API for querying density values in a layer view, we suggest you use the heatmapRendererCreator smart mapping function for creating the initial view of a heatmap, and then making renderer adjustments as needed.
Colors are assigned to each pixel based on their density value. The color ramp specified by the colorStops property maps colors to the ratio of each pixel's density value to the maxDensity. This eases the process for creating your own color stops since you don't need to know the range of density values to apply a color ramp to the renderer.
Known Limitations
Labels on layers using HeatmapRenderer are currently not supported in a 3D SceneView.
Example
layer.renderer = {
type: "heatmap",
field: "crime_count",
colorStops: [
{ ratio: 0, color: "rgba(255, 255, 255, 0)" },
{ ratio: 0.2, color: "rgba(255, 255, 255, 1)" },
{ ratio: 0.5, color: "rgba(255, 140, 0, 1)" },
{ ratio: 0.8, color: "rgba(255, 140, 0, 1)" },
{ ratio: 1, color: "rgba(255, 0, 0, 1)" }
],
minDensity: 0,
maxDensity: 500,
radius: 10
}; new HeatmapRenderer(properties)
Parameter
optionalSee the properties for a list of all the properties that may be passed into the constructor.
Show inherited properties Hide inherited properties
Property DetailsAuthoring metadata only included in renderers generated from one of the Smart Mapping creator methods, such as sizeRendererCreator.createContinuousRenderer() or colorRendererCreator.createContinuousRenderer(). This includes information from UI elements such as sliders and selected classification methods and themes. This allows the authoring clients to save specific overridable settings so that next time it is accessed via the UI, their selections can be remembered.
An array of objects describing the renderer's color ramp. The ratio of a pixel's density value to the maxDensity of the renderer is mapped to a corresponding color. The color of the first stop (i.e. the stop with the lowest ratio value) must have an alpha value of 0 for the underlying basemap to be visible in the app.
The default value is the following:
[
{ ratio: 0, color: "rgba(255, 140, 0, 0)" },
{ ratio: 0.75, color: "rgba(255, 140, 0, 1)" },
{ ratio: 0.9, color: "rgba(255, 0, 0, 1)" }
]
Inherited
Property declaredClass Stringreadonly
The name of the class. The declared class name is formatted as esri.folder.className.
The name of the attribute field used to weight the density of each heatmap point.
For example, suppose you have a layer of points representing buildings containing a field num_units for the number of units in the building (if it's an apartment complex). You could weight the heatmap renderer based on the num_units field to create a heatmap representing the density of housing units in a city.
Example
renderer.field = "num_units";Since: ArcGIS Maps SDK for JavaScript 4.24 HeatmapRenderer since 4.8, legendOptions added at 4.24.
An object providing options for describing the renderer in the Legend.
The label used to describe low density areas in the legend. If not specified, then a localized version of "Low" will display in the legend.
The label used to describe max density areas in the legend. If not specified, then a localized version of "High" will display in the legend.
Describes the variable driving the visualization. This is displayed as the title of the corresponding renderer in the Legend and takes precedence over a field alias.
Example
renderer.legendOptions = {
title: "Car crashes",
minLabel: "Few crashes",
maxLabel: "Frequent crashes"
}; maxDensity Number
Since: ArcGIS Maps SDK for JavaScript 4.24 HeatmapRenderer since 4.8, maxDensity added at 4.24.
The max density value to be assigned a color in the heatmap surface. Both minDensity and maxDensity determine how colorStops are applied to the heatmap surface. Pixels with density values above this number will be assigned the final (or hottest) color in the color ramp.
Typically, minDensity will be zero and maxDensity will be set to a higher value appropriate for the dataset. The default may not be ideal for your dataset, so this value will likely need to change.
Determining the best values for minDensity and maxDensity is an exercise left up to the developer since different types, scales, densities, and distributions of data will require different values for these properties to create a visually pleasing separation of high and low density areas appropriate for the data and the application.
Because there isn't an API for querying density values in a layer view, we suggest you use the heatmapRendererCreator smart mapping function for creating the initial view of a heatmap, and then making adjustments as needed.
Example
renderer.maxDensity = 100; minDensity Number
Since: ArcGIS Maps SDK for JavaScript 4.24 HeatmapRenderer since 4.8, minDensity added at 4.24.
The minimum density value to be assigned a color in the heatmap surface. Both minDensity and maxDensity determine how colorStops are applied to the heatmap surface. Pixels with density values below the minDensity will be excluded from the visualization.
When using a field to weight the heatmap, setting minDensity above zero might help to visually deemphasize frequently occurring but low value areas. This property does not actually filter the data or modify the calculated density value. Rather, it scales the color ramp such that a higher density value is required for a pixel to get a noticeable color.
Determining the best values for minDensity and maxDensity is an exercise left up to the developer since different types, scales, densities, and distributions of data will require different values for these properties to create a visually pleasing separation of high and low density areas appropriate for the data and the application.
Because there isn't an API for querying density values in a layer view, we suggest you use the heatmapRendererCreator smart mapping function for creating the initial view of a heatmap, and then making adjustments as needed.
Example
renderer.minDensity = 10;Since: ArcGIS Maps SDK for JavaScript 4.24 HeatmapRenderer since 4.8, radius added at 4.24.
The search radius (in points) used to create a smooth kernel surface fitted around each point. The density value is highest at the location of the point and decreases as the distance away from the point increases. The density value is 0 at the distance specified in radius from the point.
Examples
// radius in points
renderer.radius = 14;// radius in pixels
renderer.radius = "20px";// radius in points
renderer.radius = "14pt"; referenceScale Number
Since: ArcGIS Maps SDK for JavaScript 4.24 HeatmapRenderer since 4.8, referenceScale added at 4.24.
When set, the heatmap's visualization at the given scale will remain static and not change as the user zooms in and out of the view. This fixes each point's influence radius to a real-world range that doesn't change depending on the zoom level). The pixels of radius are defined at the reference scale.
A value of 0 means that the heatmap does not have a referenceScale.
The following images demonstrate how setting a reference scale will preserve a heatmap across various scales as opposed to dynamically updating on zoom.
Example
// locks the heatmap surface at the current view scale
// so that it doesn't change as the user zooms in and out
renderer.referenceScale = view.scale; type Stringreadonly
The type of renderer.
For HeatmapRenderer the type is always "heatmap".
Since: ArcGIS Maps SDK for JavaScript 4.25 HeatmapRenderer since 4.8, valueExpression added at 4.25.
An Arcade expression following the specification defined by the Arcade Visualization Profile. Expressions in HeatmapRenderer may reference field values using the $feature profile variable and must return a number.
The values returned from this expression are used to weight the density of each heatmap point.
This property is typically used as an alternative to field for data-driven visualizations.
Example
// expression calculating voter turnout based on two field values
let renderer = {
type: "heatmap", // autocasts as new HeatmapRenderer()
valueExpression: "( $feature.TOT_VOTES / $feature.REG_VOTERS ) * 100",
};Since: ArcGIS Maps SDK for JavaScript 4.25 HeatmapRenderer since 4.8, valueExpressionTitle added at 4.25.
The title identifying and describing the Arcade expression as defined in the valueExpression property. This is displayed as the title of the renderer in the Legend in the absence of a title in the legendOptions property.
Example
renderer.valueExpression = "($feature.POP / $feature.SQ_MI) * 100";
renderer.valueExpressionTitle = "Population per square mile";Show inherited methods Hide inherited methods
Method DetailsInherited
Method addHandles(handleOrHandles, groupKey)
Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, addHandles added at 4.25.
Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.
// Manually manage handles
const handle = reactiveUtils.when(
() => !view.updating,
() => {
wkidSelect.disabled = false;
},
{ once: true }
);
this.addHandles(handle);
// Destroy the object
this.destroy();
Parameters
Handles marked for removal once the object is destroyed.
groupKey *
optionalKey identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.
Creates a deep clone of the renderer.
Returns
Type Description HeatmapRenderer A deep clone of the object that invoked this method.Example
// Creates a deep clone of the first layer's renderer
let renderer = view.map.layers.at(0).renderer.clone();Inherited
Method fromJSON(json){* |null |undefined}static
Creates a new instance of this class and initializes it with values from a JSON object generated from an ArcGIS product. The object passed into the input json parameter often comes from a response to a query operation in the REST API or a toJSON() method from another ArcGIS product. See the Using fromJSON() topic in the Guide for details and examples of when and how to use this function.
Returns
Type Description * | null | undefined Returns a new instance of this class.Inherited
Method hasHandles(groupKey){Boolean}
Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, hasHandles added at 4.25.
Returns true if a named group of handles exist.
Parameter
groupKey *
optionalA group key.
Returns
Type Description Boolean Returnstrue if a named group of handles exist.
Example
// Remove a named group of handles if they exist.
if (obj.hasHandles("watch-view-updates")) {
obj.removeHandles("watch-view-updates");
}Inherited
Method removeHandles(groupKey)
Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, removeHandles added at 4.25.
Removes a group of handles owned by the object.
Parameter
groupKey *
optionalA group key or an array or collection of group keys to remove.
Example
obj.removeHandles(); // removes handles from default group
obj.removeHandles("handle-group");
obj.removeHandles("other-handle-group");RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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