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README.md

flowmap.gl

Flow map drawing layer for deck.gl. Can be used for visualizing movement of people (e.g. migration) or objects between geographic locations. The layer is rendered in WebGL and can handle large numbers of flows with a good rendering performance.

Try flowmap.blue for an easy way of publishing a flow map backed by a Google Sheets spreadsheet (no programming skills required).

Check out the live examples Storybook or the minimal example apps: with React, without React.

Features

Given an array of locations and an array of flows between these locations the layer will do the following:

  • Represent the flows as lines of varying thickness depending on the flow magnitudes
  • The flow lines are sorted so that the larger flows are drawn above
  • GeoJSON geometries of the location areas are rendered as polygons
  • Total incoming and outgoing flows for the locations are calculated and represented as circles of varying sizes.

Location totals

Both the incoming and outgoing totals for the locations are represented. A darker outline means that there are more incoming flows, a lighter outline means that there are more outgoing flows.

For instance, below we compare between the evening and the morning commuting behaviors of a large city:

Difference mode

The layer can be used to show the difference between two moments in time.

Usage

First install the required dependencies:

npm install @flowmap.gl/core deck.gl react-map-gl

Then, you can either use as a deck.gl layer or flowmap.gl as a React component:

Usage as a deck.gl layer

With this approach you can use flowmap.gl together with other deck.gl layers.

import { StaticMap } from 'react-map-gl';
import { DeckGL } from 'deck.gl';
import FlowMapLayer from '@flowmap.gl/core';             
import * as ReactDOM from 'react-dom';

ReactDOM.render(
  <DeckGL
    controller={true}
    initialViewState={{ longitude: 0, latitude: 0, zoom: 1 }}
    layers={[
      new FlowMapLayer({
        id: 'my-flowmap-layer',
        locations:
          // either array of location areas or a GeoJSON feature collection
          [{ id: 1, name: New York, lat: 40.713543, lon: -74.011219 }, 
           { id: 2, name: London, lat: 51.507425, lon: -0.127738 }, 
           { id: 3, name: Rio de Janeiro, lat: -22.906241, lon: -43.180244 }],
        flows: 
          [{ origin: 1, dest: 2, count: 42 },
           { origin: 2, dest: 1, count: 51 },
           { origin: 3, dest: 1, count: 50 },
           { origin: 2, dest: 3, count: 40 },
           { origin: 1, dest: 3, count: 22 },
           { origin: 3, dest: 2, count: 42 }],
        getFlowMagnitude: (flow) => flow.count || 0,
        getFlowOriginId: (flow) => flow.origin,
        getFlowDestId: (flow) => flow.dest,
        getLocationId: (loc) => loc.id,
        getLocationCentroid: (location) => [location.lon, location.lat],
      })
    ]}
  >
    <StaticMap mapboxApiAccessToken={mapboxAccessToken} />
  </DeckGL>,
  document.body
)

Usage as a React component

Install this additional dependency:

npm install @flowmap.gl/react
import FlowMap, { getViewStateForLocations } from '@flowmap.gl/react'

const MapVis = ({ width, height }) =>
    <div style={{ width, height }}>
        <FlowMap
          initialViewState={getViewStateForLocations(
            locations, l => l.properties.centroid, [ width, height ]
          )}
          mapboxAccessToken={mapboxAccessToken}
          flows={flows}
          locations={locations}
          getLocationId={l => l.id}
          getLocationCentroid={l => l.properties.centroid}
          getFlowOriginId={f => f.origin}
          getFlowDestId={f => f.dest}
          getFlowMagnitude={f => f.count}
          pickable={true} 
        />
    </div>

The full list of supported props:

interface Props {
  id: string;
  locations: Locations;
  flows: Flow[];
  diffMode?: boolean;
  animate?: boolean;    
  animationCurrentTime?: number;
  animationTailLength?: number;
  colors?: Colors | DiffColors;
  getLocationId?: LocationAccessor<string>;
  getLocationCentroid?: LocationAccessor<[number, number]>;
  getLocationTotalIn?: LocationAccessor<number>;
  getLocationTotalOut?: LocationAccessor<number>;
  getLocationTotalWithin?: LocationAccessor<number>;
  getFlowOriginId?: FlowAccessor<string>;
  getFlowDestId?: FlowAccessor<string>;
  getFlowMagnitude?: FlowAccessor<number>;
  getAnimatedFlowLineStaggering?: FlowAccessor<number>;
  getFlowColor?: FlowAccessor<string | undefined>;
  maxFlowThickness?: number;
  flowMagnitudeExtent?: [number, number];
  locationTotalsExtent?: [number, number];
  maxLocationCircleSize?: number;
  minPickableFlowThickness?: number;
  showTotals?: boolean;
  showLocationAreas?: boolean;
  showOnlyTopFlows?: number;
  selectedLocationIds?: string[];
  highlightedLocationId?: string;
  highlightedLocationAreaId?: string;
  highlightedFlow?: Flow;
  outlineThickness?: number;
  pickable?: boolean;
  onClick?: PickingHandler<FlowLayerPickingInfo>;
  onHover?: PickingHandler<FlowLayerPickingInfo>;
}

Development

Create an .env file in the project root containing one line:

MapboxAccessToken=<your-mapbox-access-token>

Then, run:

yarn install
yarn start
open http://localhost:6006

If you want to make changes to the core and react packages and have them automatically recompiled, run the following:

yarn core-dev
yarn react-dev

Acknowledgements

Many thanks to Philippe Voinov for his help with the first version of the FlowLinesLayer.

License

flowmap.gl Copyright 2018 Teralytics

This product includes software developed at The Apache Software Foundation (http://www.apache.org/).

Portions of this software were developed at Teralytics (http://www.teralytics.net)