Although the most straightforward way to use Torque is through either CARTO Builder, or by passing the layer’s viz.json to CARTO.js, many use cases work best with the standalone Torque.js. Assuming you have a public dataset with a date column, it is really simple to create an animated map with the library. First, you need to have a Leaflet map prepared in an HTML page:
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<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.css" />
<body>
<div id="map"></div>
<script src="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.js"></script>
<script>
var map = new L.Map('map', {
zoomControl: true,
center: [40, 0],
zoom: 3
});
L.tileLayer('http://{s}.api.cartocdn.com/base-dark/{z}/{x}/{y}.png', {
attribution: 'CARTO'
}).addTo(map);
</script>
</body>
This HTML file automatically generates the Torque.js library, which includes any Torque dependencies. For Torque to work with your table, you only need a username, the name of the table, and a CartoCSS string to style the map. Leaflet’s method addTo adds the Torque layer to the map. play runs the animation with the options specified in the CartoCSS properties.
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<script>
var CARTOCSS = [
'Map {',
'-torque-time-attribute: "date";',
'-torque-aggregation-function: "count(cartodb_id)";',
'-torque-frame-count: 760;',
'-torque-animation-duration: 15;',
'-torque-resolution: 2',
'}',
'#layer {',
' marker-width: 3;',
' marker-fill-opacity: 0.8;',
' marker-fill: #FEE391; ',
' comp-op: "lighten";',
'}'
].join('\n');
var torqueLayer = new L.TorqueLayer({
user : 'your_username',
table : 'your_table_name',
cartocss: CARTOCSS
});
torqueLayer.addTo(map);
torqueLayer.play()
</script>
You can use any kind of tile source outside CARTO, by specifying the location of a valid TileJSON file:
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var torqueLayer = new L.TorqueLayer({
tileJSON: 'http://url.to/tile.json'
cartocss: CARTOCSS
});
Optionally, it is also possible to use a custom SQL query for your visualization:
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var torqueLayer = new L.TorqueLayer({
user : 'your_username',
table : 'your_table_name',
sql_query : 'SELECT * FROM your_table_name WHERE whatever'
cartocss: CARTOCSS
});
Like in a video player, you can use animation control methods such as play, stop and pause at any point. Torque’s animator fires a change:time event each time the animation “ticks” to the next frame, and there are a number of properties and methods that can be run during playback, which are detailed in the API reference. At any point, for example, the styling of the layer’s markers can be changed using the layer.setCartoCSS('##style##').
The best way to start learning about the library is by taking a look at the examples section.