Subtract
Computes an element-wise subtraction.
Installation
$ npm install compute-subtract
For use in the browser, use browserify.
Usage
var subtract = ;
subtract( arr, x[, opts] )
Computes an element-wise subtraction. x
may be either an array
of equal length or a numeric
value.
var arr = 2 1 4 2out;out = ;// returns [ 1, 0, 3, 1 ]out = ;// returns [ 1, -1, 1, -1 ]
The function accepts the following options
:
- copy:
boolean
indicating whether to return a newarray
. Default:true
. - accessor: accessor
function
for accessing values in objectarrays
.
To mutate the input array
(e.g., when input values can be discarded or when optimizing memory usage), set the copy
option to false
.
var arr = 5 3 8 3 2 ;var out =;// returns [ 1, -1, 4, -1, -2 ]console;// returns true
Note: mutation is the array
equivalent of a minus-equal (-=
).
For object arrays
, provide an accessor function
for accessing array
values.
var data ='beep' 5'boop' 3'bip' 8'bap' 3'baz' 2;{return d 1 ;}var out =;// returns [ 1, -1, 4, -1, -2 ]
When subtracting values between two object arrays
, provide an accessor function
which accepts 3
arguments.
var data ='beep' 5'boop' 3'bip' 8'bap' 3'baz' 2;var arr ='x': 4'x': 5'x': 6'x': 5'x': 3;{if j === 0return d 1 ;return dx;}var out =;// 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
.
Examples
var subtract = ;var data = 100 ;for var i = 0; i < datalength; i++data i = Math;var out = ;console;
To run the example code from the top-level application directory,
$ node ./examples/index.js
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
Copyright
Copyright © 2014-2015. The Compute.io Authors.