signum
Signum function.
The Signum function is defined as
for any real number x
.
Installation
$ npm install compute-signum
For use in the browser, use browserify.
Usage
var signum = ;
signum( x[, options] )
Evaluates the signum function. x
may be either a number
, an array
, a typed array
, or a matrix
. Values may include NaN
, +infinity
, and -infinity
var matrix =datamatouti;out = ;// returns -1out = ;// returns [ -1, -1, 0, 0, 1, 1 ]data = -2 0 2 ;out = ;// returns [ -1, 0, 1 ]data = data ;out = ;// returns Int8Array( [ -1, 0, 1 ] )data = 6 ;for i = 0; i < 6; i++data i = i - 3;mat = ;/*[ -3 -2-1 01 2 ]*/out = ;/*[ -1 -1-1 01 1 ]*/
The function accepts the following options
:
- accessor: accessor
function
for accessingarray
values. - copy:
boolean
indicating if thefunction
should return a new data structure. Default:true
. - path: deepget/deepset key path.
- sep: deepget/deepset key path separator. Default:
'.'
.
For non-numeric arrays
, provide an accessor function
for accessing array
values.
var data ='beep' -10'boop' -1'bip' 0'bap' 1'baz' 10;{return d 1 ;}var out =;// returns [ -1, -1, 0, 1, 1 ]
To deepset an object array
, provide a key path and, optionally, a key path separator.
var data ='x':0-10'x':1-1'x':20'x':31'x':410;var out = ;/*[{'x':[0,-1]},{'x':[1,-1]},{'x':[2,0]},{'x':[3,1]},{'x':[4,1]}]*/var bool = data === out ;// returns true
By default, the function returns a new data structure. To mutate the input data structure (e.g., when input values can be discarded or when optimizing memory usage), set the copy
option to false
.
var databoolmatouti;var data = -10 -1 0 1 10 ;var out =;// returns [ -1, -1, 0, 1, 1 ]bool = data === out ;// returns truedata = 6 ;for i = 0; i < 6; i++data i = i - 3;mat = ;/*[ -3 -2-1 01 2 ]*/out =;/*[ -1 -1-1 01 1 ]*/bool = mat === out ;// returns true
When provided a typed array
or matrix
, the output data structure is of type int8
. If the copy
option is false
, the original data type of the typed array
or matrix
is preserved.
Notes
Table of results:
Value | Sign |
---|---|
x > 0 |
+1 |
x < 0 |
-1 |
0 |
0 |
-0 |
-0 |
NaN |
NaN |
The above results are compatible with an ECMAScript 6 proposal from Mozilla, which would extend the Math
object to include the method Math.sign()
. Currently, only Mozilla implements this proposal.
Examples
var matrix =signum = ;var datamatouttmpi;// Plain arrays...data = 10 ;for i = 0; i < datalength; i++data i = Math*20 - 10;out = ;// Object arrays (accessors)...{return dx;}for i = 0; i < datalength; i++data i ='x': data i;out =;// Deep set arrays...for i = 0; i < datalength; i++data i ='x': i data i x;out =;// Typed arrays...data = 10 ;for i = 0; i < datalength; i++data i = Math*20 - 10;tmp = ;out = '';for i = 0; i < datalength; i++out += tmp i ;if i < datalength-1out += ',';// Matrices...mat = ;out = ;
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.