davem8/json-stat

JSON-stat Javascript Toolkit

JSON-stat

The JSON-stat format is a simple lightweight JSON format for data dissemination. It is based in a cube model that arises from the evidence that the most common form of data dissemination is the tabular form. In this cube model, datasets are organized in dimensions. Dimensions are organized in categories.

The JSON-stat format is documented at http://json-stat.org/format/.

The goal of the JSON-stat Javascript Toolkit (JJT) is to help dealing with JSON-stat responses in Javascript.

Design principles

JSON-stat is based on a data cube information structure. The JSON-stat Javascript Toolkit exposes the data cube as a tree.

The JSON-stat tree

• Dataset
  • Dimension
    • Category
  • Data

For instance, to retrieve information about the first category of the first dimension of the first dataset in a JSON-stat response j, the JSON-stat Javascript Toolkit allows you to traverse the JSON-stat tree like this:

JSONstat( j ).Dataset( 0 ).Dimension( 0 ).Category( 0 )

General properties

• label: label of the selected element (string)
• length: number of children of the selected element (number).
• id: IDs of the children of the selected element (array).

Reading and traversing methods

These methods (except JSONstat, which is not actually a method) accept a selection argument (ID or index). If it is not provided, an array is returned with the information for every child of the selected element.

JSONstat

It reads a JSON-stat response and creates an internal jsonstat object.

JSONstat( { ... } ).length
//number of datasets in the object

JSONstat( "http://json-stat.org/samples/oecd-canada.json" ).length
//number of datasets in oecd-canada.json. Sync connection.

JSONstat( "http://json-stat.org/samples/oecd-canada.json", 
   function(){
      console.log( this.length );
   }
)
//number of datasets in oecd-canada.json. Async connection.

Dataset

It selects a particular dataset in the JSON-stat response.

JSONstat( j ).Dataset( 0 ).id //IDs of the dimensions in the first dataset

Dimension

It selects a particular dimension in a dataset in the JSON-stat response.

JSONstat( j ).Dataset( 0 ).Dimension( "time" ).label
//Label of the "time" dimension in the first dataset

JSONstat( j ).Dataset( 0 ).Dimension( "country" ).role
//Role of the "country" dimension in the first dataset

Category

It selects a particular category in a dimension in a dataset in the JSON-stat response.

JSONstat( j ).Dataset( 0 ).Dimension( "time" ).Category( 0 ).label
//Label of the first category of the "time" dimension in the first dataset

Data

When an argument is passed, selects a single cell of the data cube in the JSON-stat response. If no argument is passed, returns all the cells.

This method accepts the property "value" to get the value of a cell and "status" to get its status.

JSONstat( j ).Dataset( 0 ).Data( 0 ).value
//Value of the first cell (usually a number, but values can be of any type).

JSONstat( j ).Dataset( 0 ).Data( [ 0, 0, 0 ] ).value
//Value of the first cell in a dataset with 3 dimensions (usually a number).

JSONstat( j ).Dataset( 0 ).Data( { "metric" : "UNR", "geo" : "GR", "time" : "2014" } ).value
//Unemployment rate in Greece in 2014 (usually a number).

JSONstat( j ).Dataset( 0 ).Data( { "metric" : "UNR", "geo" : "GR", "time" : "2014" } ).status
//Status of unemployment rate in Greece in 2014.

In object arguments, single category dimensions (“constant dimensions”) can be skipped. If one and only one non-constant dimension is not specified, the result will an array with as many elements as categories in the unspecified dimension.

Transformation methods

Transformation methods get the information at a certain level of the JSON-stat tree and export it to other JSON structure for convenience.

toTable

This is a dataset method. It converts the information of a particular dataset into a JSON table. The conversion can be setup using an optional argument.

JSONstat( j ).Dataset( 0 ).toTable()
//Returns an array of arrays that exposes a tabular structure (rows and columns).
//Useful in many situations. For example, it can be a Google Visualization API input. 

JSONstat( j ).Dataset( 0 ).toTable( { field : "id" } )
//Uses ids instead of labels as column names.

JSONstat( j ).Dataset( 0 ).toTable( { vlabel : "Valor", type : "object" } )
//Returns an object of arrays (of objects) that exposes a tabular structure (rows and columns)
//in the Google DataTable format (it's the native input format of Google
//Visualization API input). The "vlabel" property is instructing the method to use
//"Valor" as the label of the values column (instead of "Value").

JSONstat( j ).Dataset( 0 ).toTable( { status : true, slabel : "Metadata" } )
//The table will include a status column with label "Metadata".

JSONstat( j ).Dataset( 0 ).toTable( { type : "arrobj" } )
//Returns an array of objects where each dimension id is a property, plus a "value" property.

JSONstat( j ).Dataset( 0 ).toTable( { type: "arrobj", content: "id" } )
//same but category ids ("AU") are used instead of labels ("Australia") even for content.

JSONstat( j ).Dataset( "canada" ).toTable(
   { type : "arrobj", content : "id" },
   function( d, i ){
      if ( d.sex === "F" && d.concept === "POP" ){
         return { age : d.age, population : d.value*1000 };
      }
   }
)
//Get only the female population by age of Canada 
//and convert values from thousands to persons.

Further information

For installation instructions, code samples, the API reference, etc., see the Wiki.