compute-euclidean-distance

Euclidean Distance
===
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> Computes the Euclidean distance between two arrays.

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

Installation

`` bash
$ npm install compute-euclidean-distance
`

For use in the browser, use browserify.

Usage

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

#### euclidean( x, y[, accessor] )

Computes the Euclidean distance between two arrays.

` javascript
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.

` javascript
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

` javascript
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,

` bash
$ 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

$3

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

` bash
$ make test
`

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

$3

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:

` bash
$ make test-cov
`

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

` bash
$ make view-cov
``

---

License

MIT license.

Copyright

Copyright © 2015. Athan Reines.

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[npm-url]: https://npmjs.org/package/compute-euclidean-distance

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[travis-url]: https://travis-ci.org/compute-io/euclidean-distance

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[coveralls-url]: https://coveralls.io/r/compute-io/euclidean-distance?branch=master

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[dependencies-url]: https://david-dm.org/compute-io/euclidean-distance

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[dev-dependencies-url]: https://david-dm.org/dev/compute-io/euclidean-distance

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[github-issues-url]: https://github.com/compute-io/euclidean-distance/issues