D3.js group() Method

With the help of d3.group() method, we can group the iterable data structure into a map where the key is defined as the element from iterable and values as an array.

Syntax:

d3.group( iterable, ...keys )

Return value: It returns the map having key as element and value as an array.

Note: To execute the below examples you have to install the d3 library by using this command prompt we have to execute the following command.

npm install d3

Example 1: In this example, we can see that by using the d3.group() method. We are able to get the map from the group iterable where the key is an element and the value as an array.

// Defining d3 contrib variable  
var d3 = require('d3');

data = [
  {name: "ABC", amount: "34.0",   date: "11/12/2015"},
  {name: "DEF", amount: "120.11", date: "11/12/2015"},
  {name: "MNO", amount: "12.01",  date: "01/04/2016"},
  {name: "XYZ", amount: "34.05",  date: "01/04/2016"}
]

var grouped_data = d3.group(data, d => d.name)

console.log(grouped_data)

Output:

Map { 'ABC' => [ { name: 'ABC', amount: '34.0', date: '11/12/2015' } ], 'DEF' => [ { name: 'DEF', amount: '120.11', date: '11/12/2015' } ], 'MNO' => [ { name: 'MNO', amount: '12.01', date: '01/04/2016' } ], 'XYZ' => [ { name: 'XYZ', amount: '34.05', date: '01/04/2016' } ] }

Example 2:

// Defining d3 contrib variable  
var d3 = require('d3');

data = [
  {name: "ABC", amount: "34.0",   date: "11/12/2015"},
  {name: "DEF", amount: "120.11", date: "11/12/2015"},
  {name: "MNO", amount: "12.01",  date: "01/04/2016"},
  {name: "XYZ", amount: "34.05",  date: "01/04/2016"}
]

var grouped_data = d3.group(data, 
        d => d.name, d => d.amount)

console.log(grouped_data)

Output:

Map {
  'ABC' => Map { '34.0' => [ [Object] ] },
  'DEF' => Map { '120.11' => [ [Object] ] },
  'MNO' => Map { '12.01' => [ [Object] ] },
  'XYZ' => Map { '34.05' => [ [Object] ] } 
}