Computes an element-wise subtraction.
npm install compute-subtractSubtract
===
[![NPM version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Coverage Status][coveralls-image]][coveralls-url] [![Dependencies][dependencies-image]][dependencies-url]
> Computes an element-wise subtraction.
`` bash`
$ npm install compute-subtract
For use in the browser, use browserify.
` javascript`
var subtract = require( 'compute-subtract' );
#### subtract( arr, x[, opts] )
Computes an element-wise subtraction. x may be either an array of equal length or a numeric value.
` javascript
var arr = [ 2, 1, 4, 2 ],
out;
out = subtract( arr, 1 );
// returns [ 1, 0, 3, 1 ]
out = subtract( arr, [ 1, 2, 3, 3 ] );
// returns [ 1, -1, 1, -1 ]
`
The function accepts the following options:
* __copy__: boolean indicating whether to return a new array. Default: true.function
* __accessor__: accessor for accessing values in object arrays.
To mutate the input array (e.g., when input values can be discarded or when optimizing memory usage), set the copy option to false.
` javascript
var arr = [ 5, 3, 8, 3, 2 ];
var out = subtract( arr, 4, {
'copy': false
});
// returns [ 1, -1, 4, -1, -2 ]
console.log( arr === out );
// returns true
`
__Note__: mutation is the array equivalent of a __minus-equal__ (-=).
For object arrays, provide an accessor function for accessing array values.
` javascript
var data = [
['beep', 5],
['boop', 3],
['bip', 8],
['bap', 3],
['baz', 2]
];
function getValue( d, i ) {
return d[ 1 ];
}
var out = subtract( data, 4, {
'accessor': getValue
});
// returns [ 1, -1, 4, -1, -2 ]
`
When subtracting values between two object arrays, provide an accessor function which accepts 3 arguments.
` javascript
var data = [
['beep', 5],
['boop', 3],
['bip', 8],
['bap', 3],
['baz', 2]
];
var arr = [
{'x': 4},
{'x': 5},
{'x': 6},
{'x': 5},
{'x': 3}
];
function getValue( d, i, j ) {
if ( j === 0 ) {
return d[ 1 ];
}
return d.x;
}
var out = subtract( data, arr, {
'accessor': getValue
});
// returns [ 1, -2, 2, -2, -1 ]
`
__Note__: j corresponds to the input array index, where j=0 is the index for the first input array and j=1 is the index for the second input array.
` javascript
var subtract = require( 'compute-subtract' );
var data = new Array( 100 );
for ( var i = 0; i < data.length; i++ ) {
data[ i ] = Math.round( Math.random()*100 );
}
var out = subtract( data, 10 );
console.log( out.join( '\n' ) );
`
To run the example code from the top-level application directory,
` bash`
$ node ./examples/index.js
Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:
` bash`
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
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:
` bash`
$ make test-cov
Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,
` bash``
$ make view-cov
---
Copyright © 2014-2015. The Compute.io Authors.
[npm-image]: http://img.shields.io/npm/v/compute-subtract.svg
[npm-url]: https://npmjs.org/package/compute-subtract
[travis-image]: http://img.shields.io/travis/compute-io/subtract/master.svg
[travis-url]: https://travis-ci.org/compute-io/subtract
[coveralls-image]: https://img.shields.io/coveralls/compute-io/subtract/master.svg
[coveralls-url]: https://coveralls.io/r/compute-io/subtract?branch=master
[dependencies-image]: http://img.shields.io/david/compute-io/subtract.svg
[dependencies-url]: https://david-dm.org/compute-io/subtract
[dev-dependencies-image]: http://img.shields.io/david/dev/compute-io/subtract.svg
[dev-dependencies-url]: https://david-dm.org/dev/compute-io/subtract
[github-issues-image]: http://img.shields.io/github/issues/compute-io/subtract.svg
[github-issues-url]: https://github.com/compute-io/subtract/issues