149 lines
3.6 KiB
Markdown
149 lines
3.6 KiB
Markdown
Hamming Distance
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===
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[![NPM version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Coverage Status][coveralls-image]][coveralls-url] [![Dependencies][dependencies-image]][dependencies-url]
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> Computes the [Hamming distance](http://en.wikipedia.org/wiki/Hamming_distance) between two sequences.
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In [information theory](http://en.wikipedia.org/wiki/Information_theory), the Hamming distance is number of differences between two sequences of the same length. These sequences may be represented as character strings, binary strings, or arrays.
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## Installation
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``` bash
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$ npm install compute-hamming
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```
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For use in the browser, use [browserify](https://github.com/substack/node-browserify).
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## Usage
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``` javascript
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var hamming = require( 'compute-hamming' );
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```
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#### hamming( a, b[, accessor] )
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Computes the [Hamming distance](http://en.wikipedia.org/wiki/Hamming_distance) between two sequences. The sequences must be either both equal length `strings` or equal length `arrays`.
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``` javascript
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var a = 'this is a string.',
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b = 'thiz iz a string.';
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var dist = hamming( a, b );
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// returns 2
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var c = [ 5, 23, 2, 5, 9 ],
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d = [ 3, 21, 2, 5, 14 ];
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dist = hamming( c, d );
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// returns 3
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```
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To compute the [Hamming distance](http://en.wikipedia.org/wiki/Hamming_distance) between nested `array` values, provide an accessor `function` for accessing `array` values.
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``` javascript
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var a = [
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{'x':2},
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{'x':4},
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{'x':5},
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{'x':3},
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{'x':8},
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{'x':2}
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];
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var b = [
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[1,3],
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[2,1],
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[3,5],
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[4,3],
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[5,7],
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[6,2]
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];
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function getValue( d, i, j ) {
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if ( j === 0 ) {
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return d.x;
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}
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return d[ 1 ];
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}
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var dist = hamming( a, b, getValue );
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// returns 3
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```
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The accessor `function` is provided three arguments:
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- __d__: current datum.
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- __i__: current datum index.
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- __j__: sequence index; e.g., sequence `a` has index `0` and sequence `b` has index `1`.
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## Examples
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To run the example code from the top-level application directory,
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``` bash
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$ node ./examples/index.js
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```
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## Tests
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### Unit
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Unit tests use the [Mocha](http://mochajs.org) test framework with [Chai](http://chaijs.com) assertions. To run the tests, execute the following command in the top-level application directory:
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``` bash
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$ make test
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```
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All new feature development should have corresponding unit tests to validate correct functionality.
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### Test Coverage
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This repository uses [Istanbul](https://github.com/gotwarlost/istanbul) as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
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``` bash
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$ make test-cov
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```
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Istanbul creates a `./reports/coverage` directory. To access an HTML version of the report,
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``` bash
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$ make view-cov
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```
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---
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## License
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[MIT license](http://opensource.org/licenses/MIT).
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## Copyright
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Copyright © 2014-2015. Athan Reines.
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[npm-image]: http://img.shields.io/npm/v/compute-hamming.svg
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[npm-url]: https://npmjs.org/package/compute-hamming
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[travis-image]: http://img.shields.io/travis/compute-io/hamming/master.svg
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[travis-url]: https://travis-ci.org/compute-io/hamming
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[coveralls-image]: https://img.shields.io/coveralls/compute-io/hamming/master.svg
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[coveralls-url]: https://coveralls.io/r/compute-io/hamming?branch=master
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[dependencies-image]: http://img.shields.io/david/compute-io/hamming.svg
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[dependencies-url]: https://david-dm.org/compute-io/hamming
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[dev-dependencies-image]: http://img.shields.io/david/dev/compute-io/hamming.svg
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[dev-dependencies-url]: https://david-dm.org/dev/compute-io/hamming
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[github-issues-image]: http://img.shields.io/github/issues/compute-io/hamming.svg
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[github-issues-url]: https://github.com/compute-io/hamming/issues
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