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HexagonLayer

The Hexagon Layer renders a hexagon heatmap based on an array of inputs. It takes the radius of hexagon bin and aggregates input objects into hexagon bins. The color and height of a hexagon are determined based on the objects it contains.

HexagonLayer is a CompositeLayer and at the moment only works with COORDINATE_SYSTEM.LNGLAT.

import DeckGL from '@deck.gl/react';
import {HexagonLayer} from '@deck.gl/aggregation-layers';

function App({data, viewState}) {
  /**
   * Data format:
   * [
   *   {COORDINATES: [-122.42177834, 37.78346622]},
   *   ...
   * ]
   */
  const layer = new HexagonLayer({
    id: 'hexagon-layer',
    data,
    pickable: true,
    extruded: true,
    radius: 200,
    elevationScale: 4,
    getPosition: d => d.COORDINATES
  });

  return <DeckGL viewState={viewState}
    layers={[layer]}
    getTooltip={({object}) => object && `${object.centroid.join(', ')}\nCount: ${object.points.length}`} />;
}

Installation

To install the dependencies from NPM:

npm install deck.gl
# or
npm install @deck.gl/core @deck.gl/layers @deck.gl/aggregation-layers
import {HexagonLayer} from '@deck.gl/aggregation-layers';
new HexagonLayer({});

To use pre-bundled scripts:

<script src="https://unpkg.com/deck.gl@^8.0.0/dist.min.js"></script>
<!-- or -->
<script src="https://unpkg.com/@deck.gl/core@^8.0.0/dist.min.js"></script>
<script src="https://unpkg.com/@deck.gl/layers@^8.0.0/dist.min.js"></script>
<script src="https://unpkg.com/@deck.gl/aggregation-layers@^8.0.0/dist.min.js"></script>
new deck.HexagonLayer({});

Properties

Inherits from all Base Layer and CompositeLayer properties.

Render Options

radius (Number, optional) transition-enabled
  • Default: 1000

Radius of hexagon bin in meters. The hexagons are pointy-topped (rather than flat-topped).

hexagonAggregator (Function, optional)
  • Default: d3-hexbin

hexagonAggregator is a function to aggregate data into hexagonal bins. The hexagonAggregator takes props of the layer and current viewport as arguments. The output should be {hexagons: [], hexagonVertices: []}. hexagons is an array of {centroid: [], points: []}, where centroid is the center of the hexagon, and points is an array of points that contained by it. hexagonVertices (optional) is an array of points define the primitive hexagon geometry.

By default, the HexagonLayer uses d3-hexbin as hexagonAggregator, see modules/layers/src/point-density-hexagon-layer/hexagon-aggregator

colorDomain (Array, optional)
  • Default: [min(colorWeight), max(colorWeight)]

Color scale input domain. The color scale maps continues numeric domain into discrete color range. If not provided, the layer will set colorDomain to the extent of aggregated weights in each hexagon. You can control how the colors of hexagons are mapped to weights by passing in an arbitrary color domain. This is useful when you want to render different data input with the same color mapping for comparison.

colorRange (Array, optional)

Specified as an array of colors [color1, color2, ...]. Each color is an array of 3 or 4 values [R, G, B] or [R, G, B, A], representing intensities of Red, Green, Blue and Alpha channels. Each intensity is a value between 0 and 255. When Alpha not provided a value of 255 is used.

colorDomain is divided into colorRange.length equal segments, each mapped to one color in colorRange.

coverage (Number, optional) transition-enabled
  • Default: 1

Hexagon radius multiplier, clamped between 0 - 1. The displayed radius of hexagon is calculated by coverage * radius. Note: coverage does not affect how objects are binned.

elevationDomain (Array, optional)
  • Default: [0, max(elevationWeight)]

Elevation scale input domain. The elevation scale is a linear scale that maps number of counts to elevation. By default it is set to between 0 and the max of aggregated weights in each hexagon. You can control how the elevations of hexagons are mapped to weights by passing in an arbitrary elevation domain. This property is useful when you want to render different data input with the same elevation scale for comparison.

elevationRange (Array, optional)
  • Default: [0, 1000]

Elevation scale output range

elevationScale (Number, optional) transition-enabled
  • Default: 1

Hexagon elevation multiplier. The actual elevation is calculated by elevationScale * getElevationValue(d). elevationScale is a handy property to scale all hexagons without updating the data.

extruded (Boolean, optional)
  • Default: false

Whether to enable cell elevation. If set to false, all cells will be flat.

upperPercentile (Number, optional) transition-enabled
  • Default: 100

Filter bins and re-calculate color by upperPercentile. Hexagons with color value larger than the upperPercentile will be hidden.

lowerPercentile (Number, optional) transition-enabled
  • Default: 0

Filter bins and re-calculate color by lowerPercentile. Hexagons with color value smaller than the lowerPercentile will be hidden.

elevationUpperPercentile (Number, optional) transition-enabled
  • Default: 100

Filter bins and re-calculate elevation by elevationUpperPercentile. Hexagons with elevation value larger than the elevationUpperPercentile will be hidden.

elevationLowerPercentile (Number, optional) transition-enabled
  • Default: 100

Filter bins and re-calculate elevation by elevationLowerPercentile. Hexagons with elevation value smaller than the elevationLowerPercentile will be hidden.

material (Object, optional)
  • Default: true

This is an object that contains material props for lighting effect applied on extruded polygons. Check the lighting guide for configurable settings.

colorAggregation (String, optional)
  • Default: 'SUM'

Defines the operation used to aggregate all data object weights to calculate a bin's color value. Valid values are 'SUM', 'MEAN', 'MIN' and 'MAX'. 'SUM' is used when an invalid value is provided.

getColorWeight and colorAggregation together determine the elevation value of each bin. If the getColorValue prop is supplied, they will be ignored.

Example 1 : Using count of data elements that fall into a bin to encode the its color
  • Using getColorValue
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getColorValue: points => points.length,
  ...
});
  • Using getColorWeight and colorAggregation
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getColorWeight: point => 1,
  colorAggregation: 'SUM'
  ...
});
Example 2 : Using mean value of 'SPACES' field of data elements to encode the color of the bin
  • Using getColorValue
function getMean(points) {
  return points.reduce((sum, p) => sum += p.SPACES, 0) / points.length;
}
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getColorValue: getMean,
  ...
});
  • Using getColorWeight and colorAggregation
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getColorWeight: point => point.SPACES,
  colorAggregation: 'SUM'
  ...
});

If your use case requires aggregating using an operation that is not one of 'SUM', 'MEAN', 'MAX' and 'MIN', getColorValue should be used to define such custom aggregation function.

elevationAggregation (String, optional)
  • Default: 'SUM'

Defines the operation used to aggregate all data object weights to calculate a bin's elevation value. Valid values are 'SUM', 'MEAN', 'MIN' and 'MAX'. 'SUM' is used when an invalid value is provided.

getElevationWeight and elevationAggregation together determine the elevation value of each bin. If the getElevationValue prop is supplied, they will be ignored.

Example 1 : Using count of data elements that fall into a bin to encode the its elevation
  • Using getElevationValue
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getElevationValue: points => points.length,
  ...
});
  • Using getElevationWeight and elevationAggregation
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getElevationWeight: point => 1,
  elevationAggregation: 'SUM'
  ...
});
Example 2 : Using maximum value of 'SPACES' field of data elements to encode the elevation of the bin
  • Using getElevationValue
function getMax(points) {
  return points.reduce((max, p) => p.SPACES > max ? p.SPACES : max, -Infinity);
}
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getElevationValue: getMax,
  ...
});
  • Using getElevationWeight and elevationAggregation
...
const layer = new HexagonLayer({
  id: 'my-hexagon-layer',
  ...
  getElevationWeight: point => point.SPACES,
  elevationAggregation: 'MAX'
  ...
});

If your use case requires aggregating using an operation that is not one of 'SUM', 'MEAN', 'MAX' and 'MIN', getElevationValue should be used to define such custom aggregation function.

Data Accessors

getPosition (Function, optional)
  • Default: object => object.position

Method called to retrieve the position of each object.

getColorWeight (Function, optional) transition-enabled
  • Default: 1

The weight of a data object used to calculate the color value for a bin.

  • If a number is provided, it is used as the weight for all objects.
  • If a function is provided, it is called on each object to retrieve its weight.
getColorValue (Function, optional) transition-enabled
  • Default: null

After data objects are aggregated into bins, this accessor is called on each bin to get the value that its color is based on. If supplied, this will override the effect of getColorWeight and colorAggregation props.

Arguments:

  • objects (Array) - a list of objects whose positions fall inside this cell.
  • objectInfo (Object) - contains the following fields:
    • indices (Array) - the indices of objects in the original data
    • data - the value of the data prop.
getElevationWeight (Function, optional) transition-enabled
  • Default: 1

The weight of a data object used to calculate the elevation value for a bin.

  • If a number is provided, it is used as the weight for all objects.
  • If a function is provided, it is called on each object to retrieve its weight.
getElevationValue (Function, optional) transition-enabled
  • Default: null

After data objects are aggregated into bins, this accessor is called on each bin to get the value that its elevation is based on. If supplied, this will override the effect of getElevationWeight and elevationAggregation props.

Arguments:

  • objects (Array) - a list of objects whose positions fall inside this cell.
  • objectInfo (Object) - contains the following fields:
    • indices (Array) - the indices of objects in the original data
    • data - the value of the data prop.

Callbacks

onSetColorDomain (Function, optional)
  • Default: ([min, max]) => {}

This callback will be called when bin color domain has been calculated.

onSetElevationDomain (Function, optional)
  • Default: ([min, max]) => {}

This callback will be called when bin elevation domain has been calculated.

Sub Layers

The HexagonLayer renders the following sublayers:

  • hexagon-cell - a ColumnLayer rendering the aggregated columns.

Source

modules/aggregation-layers/src/hexagon-layer