require(["esri/smartMapping/renderers/opacity"], (opacityVariableCreator) => { /* code goes here */ });
import * as opacityVariableCreator from "@arcgis/core/smartMapping/renderers/opacity.js";
esri/smartMapping/renderers/opacity
This object contains a helper method for generating data-driven visualizations with continuous opacity based on data returned from a field value or expression in a Layer.
The createVisualVariable() method generates an opacity visual variable with default alpha values that are optimally mapped to data values based on the statistics of the indicated field.
Known Limitations
- SceneLayers must have the
supportsRendererandsupportsLayerQuerycapabilities enabled unless a predefined statistics object is provided to thestatisticsparameter of the method. To check a SceneLayer's capabilities, use the getFieldInfoUsage() method. - You cannot generate renderers and visual variables using SQL expressions for client-side FeatureLayers in a SceneView.
- See also
Method Overview
| Name | Return Type | Summary | Object |
|---|---|---|---|
| Promise<VisualVariableResult> | This method generates an opacity visual variable with default alpha values optimally mapped to data values based on the statistics queried for the indicated field or expression. | opacity |
Method Details
-
createVisualVariable
MethodcreateVisualVariable(params){Promise<VisualVariableResult>} -
This method generates an opacity visual variable with default alpha values optimally mapped to data values based on the statistics queried for the indicated field or expression.
There are several ways this method may be called. The most common case is by providing a
layerand afield. This is the scenario where the statistics of the data aren't well known and the user doesn't know the which alpha values to map to data values. You can optionally use avalueExpressioninstead of a field to visualize features based on a numeric value returned from a script executed at runtime.The other options are provided for convenience for more involved custom visualization authoring applications. For example, if you already generated statistics in another operation, you can pass the stats in the
statisticsparameter to avoid making an extra call to the server.ParametersSpecificationparams ObjectInput parameters for generating an opacity visual variable based on data returned from a given field or expression. See the table below for details of each parameter.
Specificationlayer FeatureLayer|SceneLayer|CSVLayer|GeoJSONLayer|WFSLayer|OGCFeatureLayer|StreamLayer|OrientedImageryLayerThe layer for which the visual variable is generated.
field StringoptionalThe name of the field whose data will be queried for statistics and used for the basis of the data-driven visualization. This property is ignored if a
valueExpressionis used.normalizationField StringoptionalThe name of the field to normalize the values of the given
field. Providing a normalization field helps minimize some visualization errors and standardizes the data so all features are visualized with minimal bias due to area differences or count variation. This option is commonly used when visualizing densities.valueExpression StringoptionalAn Arcade expression following the specification defined by the Arcade Visualization Profile. Expressions may reference field values using the
$featureprofile variable and must return a number. This property overrides thefieldproperty and therefore is used instead of an inputfieldvalue.valueExpressionTitle StringoptionalText describing the value returned from the
valueExpression. This is used by the Legend widget.sqlExpression StringoptionalA SQL expression evaluating to a number.
sqlWhere StringoptionalA SQL where clause used to filter features for the statistics query. For example, this is useful in situations where you want to avoid dividing by zero as is the case with creating a predominance visualization.
legendOptions ObjectoptionalProvides options for setting a title to a field when an expression is provided instead of a field name. This title will represent the field in the Legend.
statistics SummaryStatisticsResultoptionalA statistics object generated from the summaryStatistics function. If statistics for the field have already been generated, then pass the object here to avoid making a second statistics query to the server.
minValue NumberoptionalA custom minimum value set by the user. Use this in conjunction with
maxValueto generate statistics between lower and upper bounds. This will be the lowest stop in the returned visual variable.maxValue NumberoptionalA custom maximum value set by the user. Use this in conjunction with
minValueto generate statistics between lower and upper bounds. This will be the uppermost stop in the returned visual variable.view ViewoptionalA SceneView or MapView instance is required when a
valueExpressionis specified.forBinning BooleanoptionalIndicates whether the generated renderer is for a binning visualization. If
true, then the input field(s) in this method should refer to aggregate fields defined in thefeatureReductionproperty of the layer.signal AbortSignaloptionalAllows for cancelable requests. If canceled, the promise will be rejected with an error named
AbortError. See also AbortController.ReturnsType Description Promise<VisualVariableResult> Resolves to an instance of VisualVariableResult. Exampleslet layer = new FeatureLayer({ url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/counties_politics_poverty/FeatureServer/0" }); // visualization based on field and normalization field let params = { layer: layer, field: "POP_POVERTY", normalizationField: "TOTPOP_CY" }; // when the promise resolves, apply the visual variable to the renderer opacityVariableCreator.createVisualVariable(params) .then(function(response){ let renderer = layer.renderer.clone(); renderer.visualVariables = [ response.visualVariable ]; layer.renderer = renderer; });let layer = new FeatureLayer({ url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/counties_politics_poverty/FeatureServer/0" }); // visualization based off Arcade expression let params = { layer: layer, valueExpression: "($feature.POP_POVERTY / $feature.TOTPOP_CY) * 100", view: view, valueExpressionTitle: "% of people living in poverty" }; // when the promise resolves, apply the visual variable to the renderer opacityVariableCreator.createVisualVariable(params) .then(function(response){ let renderer = layer.renderer.clone(); renderer.visualVariables = [ response.visualVariable ]; layer.renderer = renderer; });
Type Definitions
-
The result object of the createVisualVariable() method. See the table below for details of each property.
- Properties
-
visualVariable OpacityVariable
An opacity visual variable configured based on the statistics of the data.
statistics SummaryStatisticsResultBasic statistics returned from a query to the service for the given field or expression.
defaultValuesUsed BooleanIndicates whether default values are used in the absence of sufficient data and/or statistics from the layer. Default values are typically used when all features have the same field value or no value at all.
authoringInfo AuthoringInfoAuthoring information related to the creation of the visual variable. This includes information related to UI inputs from sliders and selected themes.