Histogram

AMD: require(["esri/widgets/Histogram"], (Histogram) => { /* code goes here */ });
ESM: import Histogram from "@arcgis/core/widgets/Histogram";
Class: esri/widgets/Histogram
Inheritance: Histogram Widget Accessor
Since: ArcGIS API for JavaScript 4.12

Renders a histogram to visualize the spread of a dataset based on bins representing buckets, or sub-ranges, of data. Each bin is defined by a minimum and maximum value and a total count.

You can generate the underlying histogram's bins with the histogram module. In this scenario, you can use the fromHistogramResult() helper method to conveniently create the histogram from the result object.

const params = {
  layer: povLayer,
  field: "POP_POVERTY",
  normalizationField: "TOTPOP_CY",
  numBins: 30
};

histogram(params)
  .then(function(histogramResult) {
     const histogram = Histogram.fromHistogramResult(histogramResult);
     histogram.container = "histogram";
  })
   .catch(function(error) {
     console.log("there was an error: ", error);
   });

Other properties of this widget allow to display meaningful values on the histogram, such as the average and the dataLines properties.

See the image below for a summary of the configurable options available on this slider.

Histogram with annotations

The barCreatedFunction property may be used to style the histogram bins based on the color of features in the renderer of a layer associated with the histogram.

Histogram with color

For information about gaining full control of widget styles, see the Styling topic.
See also:

Constructors

new Histogram(properties)
Parameter:
properties Object
optional

See the properties for a list of all the properties that may be passed into the constructor.

Example:
// typical usage
const histogram = new Histogram({
  bins: [{
    minValue: 0,
    maxValue: 20,
    count: 1
  }, {
    minValue: 21,
    maxValue: 40,
    count: 60
  },{
    minValue: 41,
    maxValue: 60,
    count: 239
  },{
    minValue: 61,
    maxValue: 80,
    count: 88
  },{
    minValue: 81,
    maxValue: 100,
    count: 20
  }],
  max: 100,
  min: 0,
  average: 44
});

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.
Show inherited properties Hide inherited properties
Name Type Summary Class
Numbermore details

The statistical average of the data in the histogram.

more detailsHistogram
BarCreatedFunctionmore details

Function for styling bars representing histogram bins.

more detailsHistogram
Bin[]more details

An array of objects representing each bin in the histogram.

more detailsHistogram
String|HTMLElementmore details

The ID or node representing the DOM element containing the widget.

more detailsWidget
DataLineCreatedFunctionmore details

Function that fires each time a data line is created.

more detailsHistogram
Object[]more details

When set, renders lines on the histogram that indicate important or meaningful values to the end user.

more detailsHistogram
Stringmore details

The name of the class.

more detailsAccessor
Stringmore details

The unique ID assigned to the widget when the widget is created.

more detailsWidget
Stringmore details

The widget's default label.

more detailsHistogram
LabelFormattermore details

A function used to format labels on the histogram.

more detailsHistogram
Stringmore details

Determines the orientation of the Histogram widget.

more detailsHistogram
Numbermore details

The maximum value or bound of the entire histogram.

more detailsHistogram
Numbermore details

The minimum value or bound of the entire histogram.

more detailsHistogram
Stringmore details

The state of the widget.

more detailsHistogram
HistogramViewModelmore details

The view model for the Histogram widget.

more detailsHistogram
Booleanmore details

Indicates whether the widget is visible.

more detailsWidget

Property Details

average Number

The statistical average of the data in the histogram. You would typically get this value from the avg property of SummaryStatisticsResult, which is the result of the summaryStatistics function.

When set, this value will render on the histogram with a symbol indicating it is the average.

See also:
Examples:
// sets result returned from a smart mapping method
// to the histogram
histogram.average = response.statistics.avg;
histogram.average = 34.5;
barCreatedFunction BarCreatedFunction

Function for styling bars representing histogram bins. This can be used to color bins with the same color of features in the view that fall into bins representing the same range of data.

Example:
histogram.barCreatedFunction = function(index, element){
  let bin = histogram.bins[index];
  let midValue = ((bin.maxValue - bin.minValue) / 2) + bin.minValue;
  // colors the histogram bins with a custom function
  // (not defined here for brevity of the snippet) for interpolating
  // colors from data values to match the legend
  let color = getColorFromValue(midValue);
  element.setAttribute("fill", color.toHex());
};
bins Bin[]

An array of objects representing each bin in the histogram. This information is typically returned from the histogram function.

Examples:
// sets the bins of the histogram from the bins in the histogram() result
histogram.bins = histogramResult.bins;
// Creates a histogram with 7 bins.
histogram.bins = [
  { minValue: 0, maxValue: 10, count: 4 },
  { minValue: 10.1, maxValue: 20, count: 14 },
  { minValue: 20.1, maxValue: 30, count: 9 },
  { minValue: 30.1, maxValue: 40, count: 34 },
  { minValue: 40.1, maxValue: 50, count: 351 },
  { minValue: 50.1, maxValue: 60, count: 100 },
  { minValue: 60.1, maxValue: 70, count: 1 }
];

The ID or node representing the DOM element containing the widget. This property can only be set once. The following examples are all valid use cases when working with widgets.

Examples:
// Create the HTML div element programmatically at runtime and set to the widget's container
const basemapGallery = new BasemapGallery({
  view: view,
  container: document.createElement("div")
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});
// Specify an already-defined HTML div element in the widget's container

const basemapGallery = new BasemapGallery({
  view: view,
  container: basemapGalleryDiv
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// HTML markup
<body>
  <div id="viewDiv"></div>
  <div id="basemapGalleryDiv"></div>
</body>
// Specify the widget while adding to the view's UI
const basemapGallery = new BasemapGallery({
  view: view
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});
dataLineCreatedFunction DataLineCreatedFunction

Function that fires each time a data line is created. You can use this to style individual dataLines on the data axis.

Example:
histogram.dataLineCreatedFunction = function (lineElement, labelElement, index) {
  lineElement.setAttribute("y2", "25%");
  lineElement.classList.add("line-style");
};
dataLines Object[]

When set, renders lines on the histogram that indicate important or meaningful values to the end user.

Properties:
value Number

The value on the data axis of the histogram where a line will be rendered.

label String|Number
optional

The label associated with the line.

Examples:
// will render lines at the 25th, 50th, 75th, and 99th percentiles
histogram.dataLines = [{
  value: 30,
  label: "25 pctl"
}, {
  value: 45,
  label: "50 pctl"
}, {
  value: 65,
  label: "75 pctl"
}, {
  value: 89,
  label: "99 pctl"
}];
// calculate standard deviations from mean using stats
// returned from smart mapping statistic methods
const stddevs = smartMappingUtils.getDeviationValues(stats.stddev, stats.avg, 2);
histogram.dataLines = stddevs.map(function(stddev){
  return {
    value: stddev
  };
});
declaredClass Stringreadonly inherited

The name of the class. The declared class name is formatted as esri.folder.className.

The unique ID assigned to the widget when the widget is created. If not set by the developer, it will default to the container ID, or if that is not present then it will be automatically generated.

label String

The widget's default label. This label displays when it is used within another widget, such as the Expand or LayerList widgets.

labelFormatFunction LabelFormatter

A function used to format labels on the histogram. Overrides the default label formatter.

Example:
// For thumb values, rounds each label to whole numbers.
slider.labelFormatFunction = function(value) {
  return value.toFixed(0);
}
layout String

Determines the orientation of the Histogram widget.

Possible Values:"vertical"|"horizontal"

Default Value:horizontal
Example:
histogram.layout = "vertical";
max Number

The maximum value or bound of the entire histogram. This should match the maximum bound of the last bin.

Examples:
histogram.max = 100;
// sets result returned from a smart mapping method
// to the histogram
histogram.max = response.statistics.max;
min Number

The minimum value or bound of the entire histogram. This should match the minimum bound of the first bin.

Examples:
histogram.min = 0;
// sets result returned from a smart mapping method
// to the histogram
histogram.min = response.statistics.min;
state Stringreadonly

The state of the widget.

Possible Values:"ready"|"disabled"

viewModel HistogramViewModel

The view model for the Histogram widget. This is a class that contains all the logic (properties and methods) that controls this widget's behavior. See the HistogramViewModel class to access all properties and methods on the Histogram widget.

visible Boolean inherited

Indicates whether the widget is visible.

If false, the widget will no longer be rendered in the web document. This may affect the layout of other elements or widgets in the document. For example, if this widget is the first of three widgets associated to the upper right hand corner of the view UI, then the other widgets will reposition when this widget is made invisible. For more information, refer to the CSS display value of "none".

Default Value:true
Example:
// Hides the widget in the view
widget.visible = false;

Method Overview

Show inherited methods Hide inherited methods
Name Return Type Summary Class
Stringmore details

A utility method used for building the value for a widget's class property.

more detailsWidget
more details

Destroys the widget instance.

more detailsWidget
Booleanmore details

Emits an event on the instance.

more detailsWidget
Histogrammore details

A convenience function used to create a Histogram widget instance from the result of the histogram statistics function.

more detailsHistogram
Booleanmore details

Indicates whether there is an event listener on the instance that matches the provided event name.

more detailsWidget
Booleanmore details

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).

more detailsWidget
Booleanmore details

isRejected() may be used to verify if creating an instance of the class is rejected.

more detailsWidget
Booleanmore details

isResolved() may be used to verify if creating an instance of the class is resolved.

more detailsWidget
Objectmore details

Registers an event handler on the instance.

more detailsWidget
more details

Widget teardown helper.

more detailsWidget
more details

This method is primarily used by developers when implementing custom widgets.

more detailsWidget
Objectmore details

This method is primarily used by developers when implementing custom widgets.

more detailsWidget
more details

Renders widget to the DOM immediately.

more detailsWidget
more details

This method is primarily used by developers when implementing custom widgets.

more detailsWidget
Promisemore details

when() may be leveraged once an instance of the class is created.

more detailsWidget

Method Details

classes(classNames){String}inherited

A utility method used for building the value for a widget's class property. This aids in simplifying CSS class setup.

Parameter:
classNames String|String[]|Object
repeatable

The class names.

Returns:
Type Description
String The computed class name.
See also:
Example:
// .tsx syntax showing how to set CSS classes while rendering the widget

render() {
  const dynamicIconClasses = {
    [CSS.myIcon]: this.showIcon,
    [CSS.greyIcon]: !this.showIcon
  };

  return (
    <div class={classes(CSS.root, CSS.mixin, dynamicIconClasses)} />
  );
}
destroy()inherited

Destroys the widget instance.

emit(type, event){Boolean}inherited

Emits an event on the instance. This method should only be used when creating subclasses of this class.

Parameters:
type String

The name of the event.

event Object
optional

The event payload.

Returns:
Type Description
Boolean true if a listener was notified
fromHistogramResult(result){Histogram}static

A convenience function used to create a Histogram widget instance from the result of the histogram statistics function.

Parameter:

The result of the histogram statistics function used to generate a histogram for a field or expression from a layer.

Returns:
Type Description
Histogram The histogram instance representing the histogram returned from histogram.
Example:
let colorParams = {
  layer: povLayer,
  basemap: map.basemap,
  field: "POP_POVERTY",
  normalizationField: "TOTPOP_CY",
  theme: "above-and-below"
};

let stats = null;

colorRendererCreator
  .createContinuousRenderer(colorParams)
  .then(function(response) {
     // set the renderer to the layer and add it to the map
     stats = response.statistics;

     return histogram({
       layer: povLayer,
       field: "POP_POVERTY",
       normalizationField: "TOTPOP_CY",
       numBins: 100
     });
   })
   .then(function(histogramResult) {

     let histogram = Histogram.fromHistogramResult(histogramResult);
     histogram.container = "histogram";
     histogram.average = stats.avg;
   })
   .catch(function(error) {
     console.log("there was an error: ", error);
   });
hasEventListener(type){Boolean}inherited

Indicates whether there is an event listener on the instance that matches the provided event name.

Parameter:
type String

The name of the event.

Returns:
Type Description
Boolean Returns true if the class supports the input event.
isFulfilled(){Boolean}inherited
Since: ArcGIS API for JavaScript 4.19

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).
isRejected(){Boolean}inherited
Since: ArcGIS API for JavaScript 4.19

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been rejected.
isResolved(){Boolean}inherited
Since: ArcGIS API for JavaScript 4.19

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been resolved.
on(type, listener){Object}inherited

Registers an event handler on the instance. Call this method to hook an event with a listener. See the Events summary table for a list of supported events.

Parameters:

An event or an array of events to listen for.

listener Function

The function to call when the event fires.

Returns:
Type Description
Object Returns an event handler with a remove() method that should be called to stop listening for the event(s).
Property Type Description
remove Function When called, removes the listener from the event.
Example:
view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});
own(handles)inherited

Widget teardown helper. Any handles added to it will be automatically removed when the widget is destroyed.

Parameter:

Handles marked for removal once the widget is destroyed.

postInitialize()inherited

This method is primarily used by developers when implementing custom widgets. Executes after widget is ready for rendering.

render(){Object}inherited

This method is primarily used by developers when implementing custom widgets. It must be implemented by subclasses for rendering.

Returns:
Type Description
Object The rendered virtual node.
renderNow()inherited

Renders widget to the DOM immediately.

scheduleRender()inherited

This method is primarily used by developers when implementing custom widgets. Schedules widget rendering. This method is useful for changes affecting the UI.

when(callback, errback){Promise}inherited
Since: ArcGIS API for JavaScript 4.19

when() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

Returns:
Type Description
Promise Returns a new promise for the result of callback that may be used to chain additional functions.
Example:
// Although this example uses the BasemapGallery widget, any class instance that is a promise may use when() in the same way
let bmGallery = new BasemapGallery();
bmGallery.when(function(){
  // This function will execute once the promise is resolved
}, function(error){
  // This function will execute if the promise is rejected due to an error
});

Type Definitions

BarCreatedFunction(index, element)

Function used to style or attach custom interaction to histogram bars. This function should be set to the barCreatedFunction property. It fires for each bar when it is created.

Parameters:
index Number

The index of the histogram bar. This directly corresponds to the index of the associated bin.

element SVGElement

The histogram bar element to style.

Bin

Represents the bin of a histogram. A bin consists of a minimum and a maximum value and a count. It indicates the number of values in a dataset that lie between the min and max values.

Properties:
count Number

The number of values in a dataset that are contained between the indicated minValue and maxValue.

minValue Number

The minimum value (or bound) of the bin.

maxValue Number

The maximum value (or bound) of the bin.

DataLineCreatedFunction(lineElement, labelElement, index)

Function used to style dataLines. This function should be set to the dataLineCreatedFunction property. It fires when each data line is created.

Parameters:
lineElement SVGElement

The SVG element representing the data line rendered on the histogram.

labelElement SVGElement
optional

The SVG element representing the label rendered on the histogram for the associated line element.

index Number
optional

The index of the data line.

LabelFormatter(value, type, index){String}

Function used to format labels. This function should be set to the labelFormatFunction property. This function fires every time a label is created or updated on the histogram.

Parameters:
value Number

The value for the line on the data axis.

type String
optional

The label type. Currently, the only supported type is average.

index Number
optional

The index of the data line (or value).

Returns:
Type Description
String The formatted value of the label.

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