Euclidean Distance

Computes the Euclidean distance between two arrays.

The Euclidean distance is the straight line distance between two points in Euclidean space.

Installation

$ npm install compute-euclidean-distance

For use in the browser, use browserify.

Usage

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

euclidean( x, y[, accessor] )

Computes the Euclidean distance between two arrays.

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

var d = euclidean( x, y );
// returns ~6.86

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

var x, y, d;

x = [
	[1,2],
	[2,4],
	[3,5],
	[4,3],
	[5,8],
	[6,2]
];

y = [
	{'y':3},
	{'y':1},
	{'y':5},
	{'y':-3},
	{'y':7},
	{'y':2}
];

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

d = euclidean( x, y, getValue );
// returns ~6.86

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 euclidean = require( 'compute-euclidean-distance' );

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

for ( var i = 0; i < x.length; i++ ) {
	x[ i ] = Math.round( Math.random()*10 );
	y[ i ] = Math.round( Math.random()*10 );
}

console.log( euclidean( x, y ) );

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

$ node ./examples/index.js

References

• Dahlquist, Germund and Bjorck, Ake. Numerical Methods in Scientific Computing.
• Blue, James (1978) "A Portable Fortran Program To Find the Euclidean Norm of a Vector". ACM Transactions on Mathematical Software.
• Higham, Nicholas J. Accuracy and Stability of Numerical Algorithms, Second Edition.

This module implements a one-pass algorithm proposed by S.J. Hammarling.

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. Athan Reines.