canberra-distance

Computes the Canberra distance between two arrays.

The Canberra distance defines a distance between two points in a vector space.

Installation

$ npm install compute-canberra-distance

For use in the browser, use browserify.

Usage

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

canberra( x, y[, accessor] )

Computes the Canberra distance between two arrays.

var x = [ 2, 4, 5, 3, 8, 2 ],
	y = [ 3, 1, 5, -3, 7, 2 ];

var d = canberra( x, y );
// returns ~1.87

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 dist = canberra( x, y, getValue );
// returns ~0.8

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 canberra = require( 'compute-canberra-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 = canberra( x, y );

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

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License

MIT license.

Copyright

Copyright © 2015. The Compute.io Authors.