Torque.js is an efficient and stylish rendering method to animate your data. Torque.js uses TileCubes, which are JSON representations of multidimensional data with geospatial coordinates, to render data on the client.
Torque.js is an efficient and stylish rendering method to animate your data. Torque.js uses [TileCubes](http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification), which are JSON representations of multidimensional data with geospatial coordinates, to render data on the client.
Torque.js is a JavaScript library that enables you to animate time series data. Torque.js uses tile cubes, which are JSON representations of multidimensional data with geospatial coordinates. [Tile cube specifications](http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification
) render data on the client, to optimize the transfer of temporal and categorical data for maps.
**Tip:** Torque is both a spatial and temporal aggregator. It does not plot your exact lat/lon points, it lays an invisible grid over your map, and draws one marker for each grid cell that contains points (representing an aggregation of all of the points in the grid cell). You can control the size of this grid with the CartoCSS [`-torque-resolution`](/cartodb-platform/cartocss/properties-for-torque/#torque-resolution-float) property. You are also able to control the type of aggregation with the CartoCSS [`-torque-aggregation-function`](/cartodb-platform/cartocss/properties-for-torque/#torque-aggregation-function-keyword). For more details, see the wiki page about how [Torque aggregates data](https://github.com/CartoDB/torque/wiki/How-spatial-aggregation-works).
## Implementing Torque.js
The following workflow describes how to implement Torque.js:
Workflow | Details
--- | ---
Preparing your Torque Data | When visualizing Torque style maps, it is required that you normalize your data to show a total count, or a range, of `0`-`255`. For more details, see this description about [statistical normalization](https://books.google.com/books?id=FrUQHIzXK6EC&pg=PT347&lpg=PT347&dq=choropleth+normalization&source=bl&ots=muDZhsb2jT&sig=DbomJnKedQjaKvcQgm_sVqHBt-8&hl=en&sa=X&ved=0CCYQ6AEwAjgKahUKEwje0ee8qaTHAhUCZj4KHRF5CjM#v=onepage&q=choropleth%20normalization&f=false).<br/><br/>Currently, you can only animate Torque point data. Line, polygon, and multipoint data are not supported for Torque animation.<br/><br/>**Note:** When importing Torque data, CartoDB uploads and assumes timezones are in UTC format by default. To specify a different timezone format, you must use the SQL API to import data into CartoDB.
Initialize the Torque.js Layer | Specify your username, tablename and date column to add a Torque layer to your map<br/><br/><spanclass="wrap-border"><imgsrc="/img/layout/torque/initialize_torquejs.jpg"alt="Intialize Torque.js"/></span>
Install the required CartoDB Torque Libraries | The Torque.js library interacts with CartoDB to generate the Torque tile format. If you are hosting your data on an external connector, you can modify the input parameters to redirect to any "Torque tiles service".<br/><br/>- For [basic Torque.js](#torque-library), you can export Torque tiles from your CartoDB account or use a local Postgres installation<br/><br/>- For [advanced interaction methods](#advanced-torquejs-libraries), you must download the latest Torque.js source code
Include all Torque Tiles Specifications | [Torque tile specifications](#torque-tiles-specifications) define the TorqueMap Metadata and tileset information.<br/><br/>**Note:** All Torque tile fields in the specification are required.
Customize your Animation | Style and customize your animations with [CartoCSS Properties for Torque Style Maps](/cartodb-platform/cartocss/properties-for-torque/)
## Torque Library
Torque lets you render bigdata™, time series or categorical data interactively. This is useful when you need to go beyond a static map, and create visualizations from temporal datasets. You can customize how your animated data appears in order to map such things as human movement, Twitter activity, biodiversity data, and other large-scale datasets.
- Export Torque tiles from your CartoDB account, or use a local Postgres installation [https://github.com/CartoDB/torque-gen](https://github.com/CartoDB/torque-gen)
If you are interested in using advanced interaction methods, it is a prerequisite to load the Torque.js library before using the advanced interaction methods.
- Download the [latest release](https://github.com/CartoDB/torque/releases) of the Torque.js source code
## Torque Tiles Specifications
Torque tiles are JSON representations of multidimensional data, with geospatial coordinates, that utilizes client-side resolution for rendering data. This optimizes the transfer of data for your Torque maps. Torque tile specifications are defined by two document types, Metadata and Tiles. The Metadata document describes the shared information across the Torque tile dataset. For each tile requested, there is a Tile document returned, which describes the data for that tile.
### Metadata
The TorqueMap Metadata document describes key tileset information, and includes the following fields:
Metadata Field | Description
--- | ---
`start`| start time, in steps or unix timestamp
`end`| end time, in steps or unix timestamp
`resolution`| the pixel resolution,by the power of two (1/4, 1/2,... 2, 4, 16), for a scale of 256 x 256 pixels<br/><br/>**Note:** TileCubes are typically rendered on tiles of 256 x 256 pixels. It is recommended that you choose a scale that renders perfectly along the borders of the 256 x 256 tile, otherwise there may be issues rendering artifacts. The available pixel resolutions are: `1, 2, 4, 8, 16, 32, 64, 128, 256`
`data_steps`| number of steps (in integer format)
`column_type`| "integer" or "date", default "integer"
`minzoom`| minimum zoom level, optional
`maxzoom`| max zoom level, optional
`tiles`| tile array for this set, **required**
`bounds`| [bounding box](http://wiki.openstreetmap.org/wiki/Bounding_Box) for tileset, optional
The TorqueMap Tiles document contains the required, core set of information to be rendered. This includes the number of pixels for the data, and the x and y values for each pixel.
#### The URL Schema
`http://host.com/{z}/{x}/{y}.torque.[json|bin]`
#### Tile Format
Each Torque tile is a JSON document containing an array, each of whose elements represents a point within the tile. The tile format is notated using the following format:
Tile Format | Type | Description
--- | --- |
`x`| ` integer` | x pixel coordinate in tile system reference
`y`| `integer` | y pixel coordinate in tile system reference
`steps` | | time slots when this pixel is **active**, there is data at that time
`values` | | values for each time slot<br/><br/>**Tip:** You can use the values column to store encoding categories for your data
#### Extracting Tile Results for Calculations
You can extract the pixel position, and the current time, with the Tile document results.
##### Extract the Pixel Position
To extract the pixel position for the tile, use the following calculation:
`pixel_x = x * resolution`
`pixel_y = y * resolution`
Where:
`x` and `y` are in range [0, 256/resolution] to render the final pixel position (based on 256 x2 56 tiles).
The coordinate origin for Torque tiles is the bottom left corner of the grid.
##### Extract the Current Time
To extract the current time from the Tile document, use the following calculation:
The `current_time`, `translate.start, translate.end`, and `data_steps` values are used to extract the time.
##### Tile Format Example
{% highlight js %}
[
{
x: 25,
y: 77,
values: [ 1, 10 ],
steps: [214, 215]
},
...
]
{% endhighlight %}
### Errors
All Torque tile fields in the specification are required. If a tile returns with no data or no value, _Uncaught TypeErrors_ may appear. For example, suppose you have `x, y, values` and `steps` defined, but `data_steps` are not defined in integer format, you will receive an error.
##Getting Started
Although the most straightforward way to use Torque is through either the CartoDB Editor, or by passing the layer's viz.json to [CartoDB.js](http://docs.cartodb.com/cartodb-platform/cartodb-js/getting-started/), many use cases work best with the standalone [Torque.js](https://github.com/CartoDB/torque/tree/master/dist). 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:
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.
You can use any kind of tile source outside CartoDB, by specifying the location of a [valid TileJSON](https://github.com/mapbox/tilejson-spec) file:
```javascript
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:
```javascript
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 documentation](/cartodb-platform/torque/torqueapi/). At any point, for example, the styling of the layer's markers can be changed using the `layer.setCartoCSS('##style##')`.
##Usage Examples
The best way to start learning about the library is by taking a look at some of the examples below:
* A basic example using the WWI British Navy dataset - ([view live](http://cartodb.github.io/torque/examples/navy_leaflet.html) / [source code](https://github.com/CartoDB/torque/blob/master/examples/navy_leaflet.html))
* Using tileJSON to fetch tiles - ([view live](http://cartodb.github.io/torque/examples/tilejson.html) / [source code](https://github.com/CartoDB/torque/blob/master/examples/tilejson.html))
* A car's route at the Nürburgring track mapped in Torque - ([view live](http://cartodb.github.io/torque/examples/car.html) / [source code](https://github.com/CartoDB/torque/blob/master/examples/car.html))
## Additional Torque Resources
@ -152,4 +90,4 @@ The following links contain examples, and other public information, about using
- CartoDB wiki page describing [how spatial aggregration works](https://github.com/CartoDB/torque/wiki/How-spatial-aggregation-works)
- The [Guardian's Data Blog](http://www.guardian.co.uk/news/datablog/interactive/2012/oct/01/first-world-war-royal-navy-ships-mapped) about Royal Navy ships in WWI using a Torque map
- An example of how to create a [simple Torque visualization](https://github.com/CartoDB/torque#getting-started) and the [source code](https://github.com/CartoDB/torque/blob/master/examples/navy_leaflet.html) used to create the example
- An example of how to use CartoDB.js to [add a Torque layer from a named map with auth_tokens enabled](https://gist.github.com/chriswhong/a4d1e6305ecaf2ad507a)
- An example of how to use CartoDB.js to [add a Torque layer from a named map with auth_tokens enabled](https://gist.github.com/chriswhong/a4d1e6305ecaf2ad507a)
Torque API methods can be applied when creating a visualization using the [CartoDB.js API methods](/cartodb-platform/cartodb-js/api-methods/).
# Torque API
### L.TorqueLayer(options)
One of two core classes for the Torque library - it is used to create an animated torque layer with custom settings.
#### Arguments
##### Provider options
Name | Description
--- | ---
provider | A string object, where is the data coming from. Default value is `sql_api`
options |
--- | ---
|_ sql_api |
|_ url_template |
|_ windshaft |
{% comment %}writer note_csobier: for consistency, describe options above and add ### Returns section.{% endcomment %}
A layer to be added to a Leaflet map. It works as a regular tiled layer within the Leaflet tile pane, but instead of containing `<img>` elements, it's composed of a single [`<canvas>`](https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API) where all markers are drawn.
#### Example
```js
// initialize a torque layer that uses the CartoDB account details and SQL API to pull in data
```javascript
var torqueLayer = new L.TorqueLayer({
user: 'viz2',
table: 'ow',
cartocss: CARTOCSS
cartocss: '<cartocsshere>'
});
map.addLayer(torqueLayer);
```
##### CartoDB Data Options (SQL API Provider)
#### Options
Name | Description
--- | ---
user_name | A string object, your CartoDB [account name](/cartodb-editor/your-account/#account). Default value is ```null```
table_name | A string object, the CartoDB table name where data is found (also known as a dataset.) Default value is ```null```
query | A string object, the SQL query to be performed to fetch the data. Default value is ```null```.<br/><br/>You must use this param or table, but not at the same time
cartocss | A string object, the CartoCSS style for the map. Default value is ```null```
loop | A boolean object that defines the animation loop. Default value is ```true```. If ```false```, the animation is paused when it reaches the last frame
resolution | Spatial resolution in pixels. A resolution of 1 means no spatial aggregation of the data. Its value must be a power of 2
steps | Number of steps that the animation is divided into
animationDuration | Duration, in seconds, of the animation
zIndex | Z-Index CSS property of the layer
attribution | Attribution to be added in the bottom right of the map
maxZoom | Maximum zoom for the layer.
tileSize | Size, in pixels of the tiles
##### Using a CartoDB table directly
Name | Description
--- | ---
user | A string object, your CartoDB [account name](/cartodb-editor/your-account/#account). Default value is ```null```
table | A string object, the CartoDB table name where data is found (also known as a dataset.) Default value is ```null```
##### Using a custom SQL query
Name | Description
--- | ---
query | A string object, the SQL query to be performed to fetch the data. Default value is ```null```.<br/><br/>You must use this param or table, but not at the same time
**Tip:** For a Torque category layer that is created dynamically with `cartodb.createLayer`, the SQL query must explicitly include how to build the torque_category column. You must include both the `sql` and `table_name` parameters. See this [createLayer with torque category layer](https://gist.github.com/danicarrion/dcaf6f00a71aa55134b4) example.
{% comment %}writer note_csobier: for consistency, add ### Returns section and ### Example. Note that the following table show some returns that do not make much sense to me, I did not edit the tables below, except to remove blank options columns.{% endcomment %}
##### Providing a TileJSON file
### Time Methods
Name | Description
--- | ---
tileJSON | A URL pointing to a valid [TileJSON](https://github.com/mapbox/tilejson-spec) file from which to get the Torque tile templates
`getTime()` | | current animation time (Date) | gets the real animation time
`isRunning()` | | `true`/`false` | describes whether the Torque layer is playing or is stopped
**Note:** Torque.js interprets the beginning and ending date/time from your "Time Column" as one block, then divides that up into Steps, depending on the number you set. It does not necessarily draw one frame for each row.
**Note:** Torque.js interprets the beginning and ending date/time from your "Time Column" as one block, then divides that up into [Steps](/cartodb-platform/cartocss/properties-for-torque/#torque-frame-count-number), depending on the number you set. It does not necessarily draw one frame for each row.
### Layer Control Methods
#### Layer Control Methods
Method | Options | Returns | Description
---|---|---|---
`hide()` | none | `this` | hides the Torque layer
`show()` | none| `this` | shows the Torque layer
### Style Methods
#### Style Methods
Method | Options | Returns | Description
---|---|---|---|
`setCartoCSS(cartocss)` | `cartocss string` | `this` | style the map rendering using client-side cartocss (not available with named maps)
`setCartoCSS(cartocss)` | `cartocss string` | `this` | style the map rendering using client-side CartoCSS (not available with [Named maps](/cartodb-platform/maps-api/named-maps/))
The full CartoCSS spec is not supported by Torque but instead only a limited subset with some additions related to torque rendering. To see the full list of supported parameters, read the [Torque CartoCSS documentation](/cartodb-platform/cartocss/properties-for-torque/). `value` and `zoom` variables can be used. `value` is the value of aggregation (see `countby` constructor option). `zoom` is the current zoom being rendered.
Torque supports a limited subset of CartoCSS rules defined in the [torque-reference](https://github.com/cartodb/torque-reference). To see the full list of supported rules, read the [Torque CartoCSS documentation](/cartodb-platform/cartocss/properties-for-torque/). `value` and `zoom` variables can be used. `value` is the value of aggregation. `zoom` is the current zoom being rendered.
TorqueLayer currently expects `marker` styling.
#### Example
This CartoCSS example should be `string` encoded in Javascript.
This is how a minimal example of a stylesheet for a Torque visualisation would look like.
[frame-offset = 2] { marker-fill: red; marker-width: 30; marker-fill-opacity: 0.02;}' // renders two frames ago from the current being rendered
marker-width: 3;
marker-fill-opacity: 0.8;
marker-fill: #FEE391;
}
#layer[value = 4] { // Use of the value variable, generated by the function specified in -torque-aggregation-function
marker-fill: #FABADA;
}
#layer[zoom = 12] { // Use of the zoom variable
marker-width: 10;
}
```
@ -158,10 +165,3 @@ is not a layer but is an overlay, so in order to add it to the a map use, ``laye
Name | Description
--- | ---
map | A google.maps.Map instance
## Torque Functions
Since Torque API methods can be applied when creating a visualization using the [CartoDB.js API methods](/cartodb-platform/cartodb-js/api-methods/), these [Torque Functions](https://github.com/CartoDB/cartodb.js/blob/be76b55caeeb0dfc147e3fa36628d9e215717ce5/src/vis/vis.js#L229) are available.
_**Note:** We are currently in the process of enhancing this functions and returns. A future documentation update will include complete descriptions of these Torque functions._
Carlos Matallín
9 years ago