nanstdev

Computes the sample standard deviation over an array of values ignoring any values which are not numeric.

Installation

$ npm install compute-nanstdev

For use in the browser, use browserify.

Usage

To use the module,

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

nanstdev( arr )

Computes the sample standard deviation ignoring non-numeric values.

var data = [ 10, 2, 100, NaN, 34, NaN, 0 ];

var sigma = nanstdev( data );

Examples

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

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( nanstdev( data ) );

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

$ node ./examples/index.js

Notes

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

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

console.log( nanstdev( d1 ) === nanstdev( 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.