nanhmean

!NPM versionnpm-imagenpm-url !Build Statustravis-imagetravis-url !Coverage Statuscoveralls-imagecoveralls-url !Dependenciesdependencies-imagedependencies-urlComputes the harmonic mean of an array of values ignoring any values which are not numeric.

## Installation

`$ npm install compute-nanhmean`

For use in the browser, use browserify.

## Usage

To use the module,`var nanhmean = require( 'compute-nanhmean' );`

#### nanhmean( arr )

Computes the harmonic mean ignoring non-numeric values.```
var data = [ 1, 5, NaN, 3, 4, NaN, 16 ];
var mu = nanhmean( data );
// returns ~2.7088
```

Note: only calculate the harmonic mean for positive, real numbers.

If an

`array`

contains negative numbers, the harmonic mean is nonsensical. For example, consider `x = [ 3, -3, 4 ]`

. The harmonic mean of `x`

is `12`

, while the arithmetic mean is `1.33333...`

. The harmonic mean should never be greater than the arithmetic mean. Similarly, if an

`array`

contains zero values, the harmonic mean is also zero: `1/0 --> infinity`

and `1/infinity --> 0`

. For example, consider `x = [ 0, 100, 1000, 10000 ]`

. Using the textbook definition of the harmonic mean, the mean would be `0`

, which, given `x`

, does not make sense.If an

`array`

contains elements less than or equal to `0`

, the function returns `NaN`

.## Examples

```
var nanhmean = require( 'compute-nanhmean' );
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( nanhmean( data ) );
```

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

`$ node ./examples/index.js`

## Notes

The harmonic mean of an array containing non-numeric values is equal to the harmonic 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( nanhmean( d1 ) === nanhmean( 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`