compute-manhattan-distance

Manhattan Distance

Computes the Manhattan (city block) distance between two arrays.

In an n-dimensional real vector space with a fixed Cartesian coordinate system, two points can be connected by a straight line. The sum of the line's projections onto the coordinate axes is the Manhattan distance (also known as the rectilinear distance, L1 distance, taxicab distance, or city block distance).

Installation

$ npm install compute-manhattan-distance

For use in the browser, use browserify.

Usage

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

manhattan( x, y[, accessor] )

Computes the Manhattan distance between two arrays.

var x = [ 2, 4, 5, 3, 8, 2 ],
    y = [ 3, 1, 5, -3, 7, 2 ];
 
var d = manhattan( x, y );
// returns 11

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 = manhattan( x, y, getValue );
// returns 11

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 manhattan = require( 'compute-manhattan-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( manhattan( 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

---

License

MIT license.

Copyright

Copyright © 2015. Athan Reines.