Geovisualization Developer's Guide

H.datalens. ObjectLayer

Class Summary

Presents data as points or spatial map objects with data-driven styles and client-side clustering.

[ For full details, see the Class Details ]

Class Description

Applicable for drawing interactive map objects like markers, polygons, circles and other instances of H.map.Object . Source of data can be either tiled or not tiled. Styles for objects can be parametrized with data rows and zoom level. Allows to create data-driven icons for markers like donuts or bars. Also enables clustering and data domains for visualizing up to 100k points or more.

var layer = new H.datalens.ObjectLayer(
  queryTileProvider,
  {
    rowToMapObject: function(row) {
      return new H.map.Marker(row.lat, row.lon);
    }
  }
);

Constructor Details

H.datalens.ObjectLayer (provider, options)

Parameters:
provider :: { H.map.provider.RemoteTileProvider | H.datalens.Provider | H.datalens.QueryProvider | H.datalens.QueryTileProvider }
: Data source (tiled or not)
options :: { H.datalens.ObjectLayer.Options }
: Defines data processing, clustering and data-driven styling

Property Details

static defaultDataToRows : { function( H.datalens.Service.Data ) : Array.< H.datalens.ObjectLayer.Row > }

Default value for dataToRows callback option. It represents each row as an object where property names correspond to data column names.

var layer = new H.datalens.ObjectLayer(
   provider,
   {
     dataToRows: function(data) {
       return H.datalens.ObjectLayer.defaultDataToRows(
         data
       ).filter(function() {
         ...
       })
     },
     ...
   }
);

Method Details

static createIcon (svg, options) : { H.map.Icon }

A factory method for data-driven icons. The method allows you to build an icon from SVG markup or JsonML object. Provides caching of icons with the same markup.

var metricScale = d3.linearScale();
...
var layer = new H.datalens.ObjectLayer(
  provider,
  {
    ...
    rowToStyle: function(row) {
      return {}
        icon: H.datalens.ObjectLayer.createIcon(
          [
            'svg',
            {veiwBox: [-8, -8, 8, 8]},
            ['circle', {r: metricScale(row.metric), cx: 0, cy: 0}],
          ],
          {size: 16}
        )
      }
    }
  }
);

Parameters:
svg :: { string | array }
: SVG presented as markup or JsonML Array
options :: { H.map.Icon.Options } [optional]
: Icon options (eg size and anchor). Note that the default anchor is in the middle.
options.size :: { H.math.ISize | number } [optional]
: When the icon is a square, you can define the size as a number in pixels

Returns:
:: { H.map.Icon }
: Icon which can be used for marker or cluster

static getIconCache () : { H.util.Cache }

Returns cache of icons created with the createIcon method. Can be used to clean the icon cache.

Returns:
:: { H.util.Cache }
: Icon cache

redraw ()

Force re-rendering of the layer. In the case where the callbacks passed to the layer options are not pure functions, you can call this method to force re-rendering.

updateObjectStyle (object, state)

Recalculates the style and applies it to the map object based on the new StyleState

Parameters:
object :: { H.map.Object }
: Map object
state :: { H.datalens.ObjectLayer.StyleState }
: New state

static createReusableMarker (id, args) : { H.map.Marker }

A factory method for creating reusable markers.

Parameters:
id :: { number | string }
: a unique id for the marker
args :: { object }
: arguments passed to the constructor

Returns:
:: { H.map.Marker }
: - a reusable marker