# @stdlib/math-base-special-csignum

0.2.1 • Public • Published
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# csignum

Evaluate the signum function of a double-precision complex floating-point number.

## Installation

`npm install @stdlib/math-base-special-csignum`

## Usage

`var csignum = require( '@stdlib/math-base-special-csignum' );`

#### csignum( z )

Evaluates the signum function of a double-precision complex floating-point number.

```var Complex128 = require( '@stdlib/complex-float64' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );

var v = csignum( new Complex128( -4.2, 5.5 ) );
// returns <Complex128>

var re = real( v );
// returns -0.6069136033622302

var im = imag( v );
// returns 0.79476781392673

v = csignum( new Complex128( 0.0, 0.0 ) );
// returns <Complex128>

re = real( v );
// returns 0.0

im = imag( v );
// returns 0.0

v = csignum( new Complex128( NaN, NaN ) );
// returns <Complex128>

re = real( v );
// returns NaN

im = imag( v );
// returns NaN```

## Examples

```var uniform = require( '@stdlib/random-base-uniform' ).factory;
var Complex128 = require( '@stdlib/complex-float64' );
var csignum = require( '@stdlib/math-base-special-csignum' );

var rand = uniform( -50.0, 50.0 );

var z;
var i;
for ( i = 0; i < 100; i++ ) {
z = new Complex128( rand(), rand() );
console.log( 'csignum(%s) = %s', z, csignum( z ) );
}```

## C APIs

### Usage

`#include "stdlib/math/base/special/csignum.h"`

#### stdlib_base_csignum( z )

Evaluates the signum function of a double-precision complex floating-point number.

```#include "stdlib/complex/float64.h"
#include "stdlib/complex/real.h"
#include "stdlib/complex/imag.h"

stdlib_complex128_t z = stdlib_complex128( -4.2, 5.5 );

stdlib_complex128_t out = stdlib_base_csignum( z );

double re = stdlib_real( out );
// returns -0.6069136033622302

double im = stdlib_imag( out );
// returns 0.79476781392673```

The function accepts the following arguments:

• z: `[in] stdlib_complex128_t` input value.
`stdlib_complex128_t stdlib_base_csignum( const stdlib_complex128_t z );`

### Examples

```#include "stdlib/math/base/special/csignum.h"
#include "stdlib/complex/float64.h"
#include "stdlib/complex/reim.h"
#include <stdio.h>

int main( void ) {
const stdlib_complex128_t x[] = {
stdlib_complex128( 3.14, 1.5 ),
stdlib_complex128( -3.14, -1.5 ),
stdlib_complex128( 0.0, 0.0 ),
stdlib_complex128( 0.0/0.0, 0.0/0.0 )
};

stdlib_complex128_t v;
stdlib_complex128_t y;
double re1;
double im1;
double re2;
double im2;
int i;
for ( i = 0; i < 4; i++ ) {
v = x[ i ];
y = stdlib_base_csignum( v );
stdlib_reim( v, &re1, &im1 );
stdlib_reim( y, &re2, &im2 );
printf( "csignum(%lf + %lfi) = %lf + %lfi\n", re1, im1, re2, im2 );
}
}```

## Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

See LICENSE.

## Copyright

Copyright © 2016-2024. The Stdlib Authors.

## Package Sidebar

### Install

`npm i @stdlib/math-base-special-csignum`

### Repository

github.com/stdlib-js/math-base-special-csignum

stdlib.io

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