L2 norm

Computes the L2 norm (Euclidean norm) of an array.

Installation

$ npm install compute-l2norm

For use in the browser, use browserify.

Usage

var l2norm = require( 'compute-l2norm' );

l2norm( arr[, accessor] )

Computes the L2 norm (Euclidean norm) of an array.

var data = [ 2, 7, 3, -3, 9 ];

var norm = l2norm( data );
// returns ~12.3288

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

var data = [
	['beep', 3],
	['boop', 4]
];

function getValue( d, i ) {
	return d[ 1 ];
}

var norm = l2norm( data, getValue );
// returns 5

If provided an empty array, the function returns null.

Examples

var l2norm = require( 'compute-l2norm' );

var data = new Array( 1000 );
for ( var i = 0; i < data.length; i++ ) {
	data[ i ] = Math.random() * 100;
}

console.log( l2norm( data ) );

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

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License

MIT license.

Copyright

Copyright © 2014-2015. Athan Reines.