Data

Akin to Vega’s data model, the basic data model used by Vega-Lite is tabular data, similar to a spreadsheet or a database table. Individual data sets are assumed to contain a collection of records, which may contain any number of named data fields.

{
  "data": ... ,       // data
  "mark": ... ,
  "encoding": ... ,
  ...
}

Vega-Lite’s optional top-level data property describes the visualization’s data source as part of the specification, which can be either inline data (values) or a URL from which to load the data (url). Alternatively, if the data property is not specified, the data source can be bound at runtime.

Here is a list of all properties describing data source:

Property	Type	Description
values	Array	Array of object that maps field names to their values.
url	String	A URL from which to load the data set. Use the `format.type` property to ensure the loaded data is correctly parsed.
format	Object	Type of input data: `"json"`, `"csv"`, `"tsv"`. The default format type is determined by the extension of the file url. If no extension is detected, `"json"` will be used by default.

Inline Data

Inline Data can be specified using values property. For example, the following specification embeds an inline data table with two rows and two columns (a and b).

Data from URL

Data can be specified from url using the url property. In addition, format of the input data can be optionally specified using formatType property.

For example, the following specification loads data from a relative url: data/cars.json. Note that the format type is implicitly json by default.

Format

The format object has the following properties:

Name	Type	Description
type	String	Type of The currently supported formats are `json` (JavaScript Object Notation), `csv` (comma-separated values), `tsv` (tab-separated values), `topojson`. • For JSON file, Vega-Lite assumes row-oriented data, where each row is an object with named attributes. • For TSV/CSV, the properties of the loaded JSON object are taken from the values of the first row of the file. • For TopoJSON, the input file must contain valid TopoJSON data. The TopoJSON input is then converted into a GeoJSON format for use within Vega. You can also configure `feature` and `mesh` properties for TopoJSON.
parse	Object	By default, Vega-lite automatically determines how to parse the input data based on encoded and filtered field. This property provides name-value pairs, where the name is the name of the attribute, and the value is the desired data type (one of `"number"`, `"boolean"` or `"date"`) for customizing data parsing. For example, `"parse": {"modified_on":"date"}` ensures that the `modified_on` value in each row of the input data is parsed as a Date value. (See Datalib’s `dl.read.types` method for more information.) This property can be useful for defining data types for fields used in `calculate` or `filter` expression.
property	String	(JSON only) The JSON property containing the desired data. This parameter can be used when the loaded JSON file may have surrounding structure or meta-data. For example `"property": "values.features"` is equivalent to retrieving `json.values.features` from the loaded JSON object.
feature	String	(TopoJSON only) The name of the TopoJSON object set to convert to a GeoJSON feature collection. For example, in a map of the world, there may be an object set named `"countries"`. Using the feature property, we can extract this set and generate a GeoJSON feature object for each country.
mesh	String	(TopoJSON only) The name of the TopoJSON object set to convert to a mesh. Similar to the `feature` option, `mesh` extracts a named TopoJSON object set. Unlike the `feature` option, the corresponding geo data is returned as a single, unified mesh instance, not as individual GeoJSON features. Extracting a mesh is useful for more efficiently drawing borders or other geographic elements that you do not need to associate with specific regions such as individual countries, states or counties.