Premature merge.

README.md

@@ -2,7 +2,7 @@ L2 norm
 ===
 [![NPM version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Coverage Status][coveralls-image]][coveralls-url] [![Dependencies][dependencies-image]][dependencies-url]
 
-> Computes the L2 norm ([Euclidean norm](http://en.wikipedia.org/wiki/Norm_(mathematics))) of an array of values.
+> Computes the L2 norm ([Euclidean norm](http://en.wikipedia.org/wiki/Norm_(mathematics))) of an array.
 
 
 ## Installation
@@ -16,14 +16,13 @@ For use in the browser, use [browserify](https://github.com/substack/node-browse
 
 ## Usage
 
-
 ``` javascript
 var l2norm = require( 'compute-l2norm' );
 ```
 
 #### l2norm( arr[, accessor] )
 
-Computes the _L2_ norm (Euclidean norm) of an `array` of values.
+Computes the _L2_ norm (Euclidean norm) of an `array`.
 
 ``` javascript
 var data = [ 2, 7, 3, -3, 9 ];
@@ -44,10 +43,12 @@ function getValue( d, i ) {
 	return d[ 1 ];
 }
 
-var res = l2norm( data, getValue );
+var norm = l2norm( data, getValue );
 // returns 5
 ```
 
+If provided an empty `array`, the function returns `null`.
+
 
 ## Examples
 

examples/index.js

@@ -1,8 +1,10 @@
+'use strict';
+
 var l2norm = require( './../lib' );
 
 var data = new Array( 1000 );
 for ( var i = 0; i < data.length; i++ ) {
 	data[ i ] = Math.random() * 100;
 }
 
-console.log( l2norm( data ) );
+console.log( l2norm( data ) );

lib/index.js

@@ -1,30 +1,30 @@
 'use strict';
 
-// L2NORM //
+// MODULES //
 
 var isArray = require( 'validate.io-array' ),
 	isFunction = require( 'validate.io-function' );
 
 
+// L2NORM //
+
 /**
-* FUNCTION: l2norm( arr )
-*	Calculates the L2 norm (Euclidean norm) of an array of values.
+* FUNCTION: l2norm( arr[, accessor] )
+*	Calculates the L2 norm (Euclidean norm) of an array.
 *
-* @param {Array} arr - array of values
+* @param {Array} arr - input array
 * @param {Function} [accessor] - accessor function for accessing array values
-* @returns {Number} L2 norm
+* @returns {Number|Null} L2 norm or null
 */
 function l2norm( arr, clbk ) {
 	if ( !isArray( arr ) ) {
 		throw new TypeError( 'l2norm()::invalid input argument. Must provide an array.  Value: `' + arr + '`.' );
 	}
-
 	if ( arguments.length > 1 ) {
 		if ( !isFunction( clbk ) ) {
 			throw new TypeError( 'l2norm()::invalid input argument. Accessor must be a function. Value: `' + clbk + '`.' );
 		}
 	}
-
 	var len = arr.length,
 		t = 0,
 		s = 1,
@@ -33,13 +33,13 @@ function l2norm( arr, clbk ) {
 		abs,
 		i;
 
+	if ( !len ) {
+		return null;
+	}
 	if ( clbk ) {
 		for ( i = 0; i < len; i++ ) {
 			val = clbk( arr[ i ], i );
-			abs = val;
-			if ( abs < 0 ) {
-				abs = -abs;
-			}
+			abs = ( val < 0 ) ? -val : val;
 			if ( abs > 0 ) {
 				if ( abs > t ) {
 					r = t / val;
@@ -54,10 +54,7 @@ function l2norm( arr, clbk ) {
 	} else {
 		for ( i = 0; i < len; i++ ) {
 			val = arr[ i ];
-			abs = val;
-			if ( abs < 0 ) {
-				abs = -abs;
-			}
+			abs = ( val < 0 ) ? -val : val;
 			if ( abs > 0 ) {
 				if ( abs > t ) {
 					r = t / val;

package.json

@@ -35,7 +35,13 @@
     "linear algebra",
     "norm",
     "euclidean norm",
-    "l2norm"
+    "l2norm",
+    "l2 distance",
+    "euclidean length",
+    "length",
+    "distance",
+    "array",
+    "vector"
   ],
   "bugs": {
     "url": "https://github.com/compute-io/l2norm/issues"

test/test.js

@@ -1,3 +1,4 @@
+/* global require, describe, it */
 'use strict';
 
 // MODULES //
@@ -25,15 +26,15 @@ describe( 'compute-l2norm', function tests() {
 
 	it( 'should throw an error if not provided an array', function test() {
 		var values = [
-				'5',
-				5,
-				null,
-				undefined,
-				NaN,
-				true,
-				{},
-				function(){}
-			];
+			'5',
+			5,
+			null,
+			undefined,
+			NaN,
+			true,
+			{},
+			function(){}
+		];
 
 		for ( var i = 0; i < values.length; i++ ) {
 			expect( badValue( values[i] ) ).to.throw( TypeError );
@@ -68,6 +69,10 @@ describe( 'compute-l2norm', function tests() {
 		}
 	});
 
+	it( 'should return null if provided an empty array', function test() {
+		assert.isNull( l2norm( [] ) );
+	});
+
 	it( 'should return the L2 norm', function test() {
 		var data, expected;