Squarify

This package is a TypeScript implementation (with no external runtime dependencies) of Bruls et al.'s squarified tree map algorithm. If you're interested in how the algorithm works, I explain it in details in an article on my blog.

This is a "battle-tested" implementation and is currently used to calculate the layout of the trade tree map in the Atlas of Economic Complexity, a data visualizsation tool used by 15,000 unique visitors per month.

Unlike other JavaScript implementations, it is written in clear, readable code and backed up by unit tests (98% coverage).

As a strong believer in composable software, I deliberately made this package minimal. It only performs the layout step. You are free to use the output to render whichever way you want.

Installation

npm install --save squarify

Usage

Input

The default export of this package is a function that expects two parameters:

• An array of input data. It's a recursive data structure where each element has this shape:

type Input<Custom> = {
    value: number;
    children?: Input<Custom>[];
} & Custom;

where Custom describes the type of any extra data the user wants to attach to each node. This data will be passed through to the result.

• value is a strictly positive (i.e. non-zero) number and must be provided. The displayed area of any node is proportional to its value. The sum of the value of a node's leaves must equal the value of the node itself. At every level of nesting of data, all array items must be already sorted in descending value order.
• children is optional and indicates whether a datum is a node (children is an array) or a leaf (children is undefined).
• Your data also shouldn't contain the property normalizedValue because it is used internally by the package.

Sample input data (note that the name and color fields in the input data, which are user-defined and optional, will be passed through to the result):

[{
  name: 'Azura', value: 6, color: 'red',
}, {
  name: 'Seth', value: 5, color: '',
  children: [
    {
      name: 'Noam', value: 3, color: 'orange',
    },
    {
      name: 'Enos', value: 2, color: 'yellow',
    },
  ]
}, {
  name: 'Awan', value: 5, color: '',
  children: [{
      name: 'Enoch', value: 5, color: 'green',
  }]
}, {
  name: 'Abel', value: 4, color: 'blue',
}, {
  name: 'Cain', value: 1, color: 'indigo',
}]

• A rectangle that this algorithm will try to fit the tree map into. It should be specified as an object with this shape:

interface Container {
    x0: number;
    y0: number;
    x1: number;
    y1: number;
}

where (x0, y0) and (x1, y1) are the coordinates of the top-left and bottom-right corners of the rectangle, respectively (x increases going rightward and y increases going downward on the page). Sample data:

{x0: 0, y0: 0, x1: 100, y1: 50};

Output

The output is an array of layout rectangles. Each rectangle has this shape:

interface Result {
  x0: number;
  y0: number;
  x1: number;
  y1: number;
  value: number,
  normalizedValue: number
} & Custom

where

• x0, y0, x1, y1 are the coordinates of the top-left and bottom-right corners of the rectangle.
• normalizedValue is a value used internally, which you can ignore.
• value is the same one from the original input data.
• Any extra properties in the input are passed through to this rectangle. Also note that the algorithm also flatten the output such that only leaves in the original data will appear in the output.

Sample output for the above sample input:

[
  {x0: 0, y0: 0, x1: 41.66, y1: 35, name: 'Noam', value: 3, color: 'orange'},
  {x0: 0, y0: 35, x1: 41.66, y1: 50, name: 'Enos', value: 2, color: 'yellow'},
  {x0: 41.66, y0: 0, x1: 70.83, y1: 50, name: 'Abel', value: 4, color: 'blue'},
  {x0: 70.83, y0: 0, x1: 100, y1: 28.57, name: 'Azura', value: 6, color: 'red'},
  {x0: 70.83, y0: 0, x1: 90.27, y1: 50, name: 'Enoch', value: 5, color: 'green'},
  {x0: 90.27, y0: 28.57, x1: 100, y1: 50, name: 'Cain', value: 1, color: 'indigo'}
]

Sample input

This is sample usage in a TypeScript file:

import squarify, {
  Input
} from 'squarify'

interface Custom {
  name: string;
  color: string;
}
const data: Input<Custom>[] = [{
  name: 'Azura', value: 6, color: 'red',
}, {
  name: 'Seth', value: 5, color: '',
  children: [
    {
      name: 'Noam', value: 3, color: 'orange',
    },
    {
      name: 'Enos', value: 2, color: 'yellow',
    },
  ]
}, {
  name: 'Awan', value: 5, color: '',
  children: [{
      name: 'Enoch', value: 5, color: 'green',
  }]
}, {
  name: 'Abel', value: 4, color: 'blue',
}, {
  name: 'Cain', value: 1, color: 'indigo',
}];

const container = {x0: 0, y0: 0, x1: 100, y1: 50};

const output = squarify<Custom>(data, container);

This is a sample in JavaScript:

import squarify from 'squarify'
// Or `const squarify = require('squarify')` in NodeJS.

const data = [{
  name: 'Azura', value: 6, color: 'red',
}, {
  name: 'Seth', value: 5, color: '',
  children: [
    {
      name: 'Noam', value: 3, color: 'orange',
    },
    {
      name: 'Enos', value: 2, color: 'yellow',
    },
  ]
}, {
  name: 'Awan', value: 5, color: '',
  children: [{
      name: 'Enoch', value: 5, color: 'green',
  }]
}, {
  name: 'Abel', value: 4, color: 'blue',
}, {
  name: 'Cain', value: 1, color: 'indigo',
}];

const container = {x0: 0, y0: 0, x1: 100, y1: 50};

const output = squarify(data, container);

Contributing

Please see the contributing guide if you are interested in helping.