compute-cosine-distance v1.0.0

Cosine Distance

Computes the cosine distance between two arrays.

Cosine similarity defines vector similarity in terms of the angle separating two vectors.

The computed similarity resides on the interval [-1,1], where vectors with the same orientation have a similarity equal to 1, orthogonal orientation a similarity equal to 0, and opposite orientation a similarity equal to -1. The cosine distance seeks to express vector dissimilarity in positive space and does so by subtracting the similarity from 1.

Installation

$ npm install compute-cosine-distance

For use in the browser, use browserify.

Usage

var distance = require( 'compute-cosine-distance' );

distance( x, y, accessor )

Computes the cosine distance between two arrays.

var x = [ 5, 23, 2, 5, 9 ],
    y = [ 3, 21, 2, 5, 14 ];

var d = distance( x, y );
// returns ~0.025

For object arrays, provide an accessor function for accessing numeric values.

var x = [
	{'x':2},
	{'x':4},
	{'x':5}
];

var y = [
	[1,3],
	[2,1],
	[3,5]
];

function getValue( d, i, j ) {
	if ( j === 0 ) {
		return d.x;
	}
	return d[ 1 ];
}

var d = distance( x, y, getValue );
// returns ~0.118

The accessor function is provided three arguments:

• d: current datum.
• i: current datum index.
• j: array index; e.g., array x has index 0, and array y has index 1.

If provided empty arrays, the function returns null.

Examples

var distance = require( 'compute-cosine-distance' );

var x = new Array( 100 ),
	y = new Array( 100 ),
	d;

for ( var i = 0; i < x.length; i++ ) {
	x[ i ] = Math.round( Math.random()*100 );
	y[ i ] = Math.round( Math.random()*100 );
}
d = distance( x, y );

console.log( d );

To run the example code from the top-level application directory,

$ node ./examples/index.js

Tests

Unit

Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

License

MIT license.

Copyright

Copyright © 2015. Philipp Burckhardt.