Histogram

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

See also

histogram

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

Type	Summary	Class
Number	The statistical average of the data in the histogram. more details	Histogram
BarCreatedFunction	Function for styling bars representing histogram bins. more details	Histogram
Bin []	An array of objects representing each bin in the histogram. more details	Histogram
String\|HTMLElement	The ID or node representing the DOM element containing the widget. more details	Widget
DataLineCreatedFunction	Function that fires each time a data line is created. more details	Histogram
Object []	When set, renders lines on the histogram that indicate important or meaningful values to the end user. more details	Histogram
String	The name of the class. more details	Accessor
String	The unique ID assigned to the widget when the widget is created. more details	Widget
String	The widget's default label. more details	Histogram
LabelFormatter	A function used to format labels on the histogram. more details	Histogram
String	Determines the orientation of the Histogram widget. more details	Histogram
Number	The maximum value or bound of the entire histogram. more details	Histogram
Number	The minimum value or bound of the entire histogram. more details	Histogram
String	The state of the widget. more details	Histogram
HistogramViewModel	The view model for the Histogram widget. more details	Histogram
Boolean	Indicates whether the widget is visible. more details	Widget

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

summaryStatistics

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 }
];

container String|HTMLElement inherited

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.

id String inherited

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

Return Type	Summary	Class
	Adds one or more handles which are to be tied to the lifecycle of the object. more details	Accessor
String	A utility method used for building the value for a widget's `class` property. more details	Widget
	Destroys the widget instance. more details	Widget
Boolean	Emits an event on the instance. more details	Widget
Histogram	A convenience function used to create a Histogram widget instance from the result of the histogram statistics function. more details	Histogram
Boolean	Indicates whether there is an event listener on the instance that matches the provided event name. more details	Widget
Boolean	Returns true if a named group of handles exist. more details	Accessor
Boolean	`isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). more details	Widget
Boolean	`isRejected()` may be used to verify if creating an instance of the class is rejected. more details	Widget
Boolean	`isResolved()` may be used to verify if creating an instance of the class is resolved. more details	Widget
Object	Registers an event handler on the instance. more details	Widget
	Adds one or more handles which are to be tied to the lifecycle of the widget. more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Removes a group of handles owned by the object. more details	Accessor
Object	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Renders widget to the DOM immediately. more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	Widget
Promise	`when()` may be leveraged once an instance of the class is created. more details	Widget

Method Details

addHandles(handleOrHandles, groupKey)inherited Since: ArcGIS Maps SDK for JavaScript 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

handleOrHandles WatchHandle|WatchHandle []

Handles marked for removal once the object is destroyed.

groupKey *

optional

Key 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.

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

Guide - Custom widget basics (rendering)

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

result HistogramResult

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.

hasHandles(groupKey){Boolean}inherited Since: ArcGIS Maps SDK for JavaScript 4.25

Returns true if a named group of handles exist.

Parameter

groupKey *

optional

A group key.

Returns

Type	Description
Boolean	Returns `true` 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");
}

isFulfilled(){Boolean}inherited Since: ArcGIS Maps SDK 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 Maps SDK 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 Maps SDK 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.

Parameters

type String|String []

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(handleOrHandles)inherited Since: ArcGIS Maps SDK for JavaScript 4.24 Deprecated since 4.28 Use addHandles() instead.

Adds one or more handles which are to be tied to the lifecycle of the widget. The handles will be removed when the widget is destroyed.

const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true}
);

this.own(handle); // Handle gets removed when the widget is destroyed.

Parameter

handleOrHandles WatchHandle|WatchHandle []

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.

removeHandles(groupKey)inherited Since: ArcGIS Maps SDK for JavaScript 4.25

Removes a group of handles owned by the object.

Parameter

groupKey *

optional

A 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");

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 Maps SDK 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`.

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.

ArcGIS Maps SDK for JavaScriptAPI Reference

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