nangmean

Computes the geometric mean of an array of values ignoring any values which are not numeric.

Installation

$ npm install compute-nangmean

For use in the browser, use browserify.

Usage

To use the module,

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

nangmean( arr )

Computes the geometric mean ignoring non-numeric values.

var data = [ 1, 5, NaN, 2, 3, NaN, 7 ];

var mu = nangmean( data );
// returns ~2.914

Note: only calculate the geometric mean over an array containing positive numbers. The textbook formula for calculating the geometric mean involves taking the product of all array elements. If one element is 0, then the product is 0, even if all other values are >>> 0, yielding a nonsensical geometric mean (and measure of the central tendency). Nonsensical results also arise when an array contains negative values leading to a product without positive roots and a geometric mean which does not map to the measure's geometric interpretation. For more information, see Handbook of Parametric and Nonparametric Statistical Procedures: Third Edition by David J. Sheskin.

If an array contains numeric values less than or equal to 0, the function returns NaN.

Examples

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

var data = new Array( 1000 );
for ( var i = 0; i < data.length; i++ ) {
	if ( i%5 === 0 ) {
		data[ i ] = NaN;
	} else {
		data[ i ] = Math.random() * 100;
	}
}

console.log( nangmean( data ) );

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

$ node ./examples/index.js

Notes

The geometric mean of an array containing non-numeric values is equal to the geometric mean of an equivalent array which contains only the numeric values. Hence,

var d1 = [ 1, NaN, 2, 3, NaN ],
	d2 = [ 1, 2, 3 ];

console.log( nangmean( d1 ) === nangmean( d2 ) );
// returns true

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 © 2014. Athan Reines.