nangmean

!NPM versionnpm-imagenpm-url !Build Statustravis-imagetravis-url !Coverage Statuscoveralls-imagecoveralls-url !Dependenciesdependencies-imagedependencies-urlComputes 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`