Hamming Distance

Computes the Hamming distance between two sequences.

In 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.

Installation

$ npm install compute-hamming

For use in the browser, use browserify.

Usage

var hamming = require( 'compute-hamming' );

hamming( a, b[, accessor] )

Computes the Hamming distance between two sequences. The sequences must be either both equal length strings or equal length arrays.

var a = 'this is a string.',
	b = 'thiz iz a string.';

var dist = hamming( a, b );
// returns 2

var c = [ 5, 23, 2, 5, 9 ],
	d = [ 3, 21, 2, 5, 14 ];

dist = hamming( c, d );
// returns 3

To compute the Hamming distance between nested array values, provide an accessor function for accessing array values.

var a = [
	{'x':2},
	{'x':4},
	{'x':5},
	{'x':3},
	{'x':8},
	{'x':2}
];

var b = [
	[1,3],
	[2,1],
	[3,5],
	[4,3],
	[5,7],
	[6,2]
];

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

var dist = hamming( a, b, getValue );
// returns 3

The accessor function is provided three arguments:

d: current datum.
i: current datum index.
j: sequence index; e.g., sequence a has index 0 and sequence b has index 1.

Examples

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.

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