README.md

nanmedian

Computes the median of an array ignoring non-numeric values.

Installation

$ npm install compute-nanmedian

For use in the browser, use browserify.

Usage

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

nanmedian( arr[, options] )

Computes the median of an array ignoring non-numeric values. For unsorted primitive arrays,

var unsorted = [ 5, null, 3, 2, 4, null ];

var m1 = nanmedian( unsorted );
// returns 3.5

The function accepts two options:

• sorted: boolean flag indicating if the input array is sorted in ascending order. Default: false.
• accessor: accessor function for accessing values in object arrays.

If the input array is already sorted in ascending order, set the sorted option to true.

var sorted = [ null, 2, 3, 4, null, 5 ];

var m2 = nanmedian( sorted, { 'sorted': true });
// returns 3.5

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

var data = [
	[1,5],
	[2,null],
	[3,3],
	[4,2],
	[5,4],
	[6,null]
];

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

var m3 = nanmedian( data, {
	'sorted': false,
	'accessor': getValue
});
// returns 3.5

Note: if provided an array which does not contain any numeric values, the function returns null.

Examples

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

var data = new Array( 1001 );
for ( var i = 0; i < data.length; i++ ) {
	if ( i % 2 === 0 ) {
		data[ i ] = null;
	} else {
		data[ i ] = Math.round( Math.random() * 100 );
	}
}
console.log( nanmedian( data ) );

To run the example code from the top-level application directory,

$ node ./examples/index.js

Notes

If provided an unsorted input array, the function is O( N log(N) ), where N is the array length. If the array is already sorted in ascending order, the function is O(N) as the function needs to make a single linear pass to remove non-numeric values from the array.

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 © 2015. Philipp Burckhardt.