Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/stdlib-js/blas-base-zdscal

Scale a double-precision complex floating-point vector by a double-precision floating-point constant.
https://github.com/stdlib-js/blas-base-zdscal

algebra array blas complex complex128 javascript level-1 linear math mathematics ndarray node node-js nodejs scale stdlib subroutines typed vector zdscal

Last synced: about 6 hours ago
JSON representation

Scale a double-precision complex floating-point vector by a double-precision floating-point constant.

Awesome Lists containing this project

README 

        



  

    About stdlib...

  

  
We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.


  
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.


  
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.


  
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!



# zdscal



[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] 



> Scale a double-precision complex floating-point vector by a double-precision floating-point constant.



## Installation



```bash

npm install @stdlib/blas-base-zdscal

```



Alternatively,



-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).



The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.



To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.



## Usage



```javascript

var zdscal = require( '@stdlib/blas-base-zdscal' );

```



#### zdscal( N, da, zx, strideZX )



Scales a double-precision complex floating-point vector by a double-precision floating-point constant.



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );

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

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



var zx = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );



zdscal( 3, 2.0, zx, 1 );



var z = zx.get( 0 );

// returns 



var re = real( z );

// returns 2.0



var im = imag( z );

// returns 2.0

```



The function has the following parameters:



-   **N**: number of indexed elements.

-   **da**: scalar constant.

-   **zx**: input [`Complex128Array`][@stdlib/array/complex128].

-   **strideZX**: stride length for `zx`.



The `N` and stride parameters determine which elements in `zx` are scaled by `da`. For example, to scale every other element in `zx` by `da`,



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );

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

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



var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );



zdscal( 2, 2.0, zx, 2 );



var z = zx.get( 2 );

// returns 



var re = real( z );

// returns 10.0



var im = imag( z );

// returns 12.0

```



Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );

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

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



// Initial array:

var zx0 = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );



// Create an offset view:

var zx1 = new Complex128Array( zx0.buffer, zx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element



// Scale every element in `zx1`:

zdscal( 3, 2.0, zx1, 1 );



var z = zx0.get( 0 );

// returns 



var re = real( z );

// returns 1.0



var im = imag( z );

// returns 2.0



z = zx0.get( 1 );

// returns 



re = real( z );

// returns 6.0



im = imag( z );

// returns 8.0

```



#### zdscal.ndarray( N, da, zx, strideZX, offsetZX )



Scales a double-precision complex floating-point vector by a double-precision floating-point constant using alternative indexing semantics.



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );

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

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



var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );



zdscal.ndarray( 3, 2.0, zx, 1, 0 );



var z = zx.get( 0 );

// returns 



var re = real( z );

// returns 2.0



var im = imag( z );

// returns 4.0

```



The function has the following additional parameters:



-   **offsetZX**: starting index for `zx`.



While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to scale every other element in the input strided array starting from the second element,



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );

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

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



var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );



zdscal.ndarray( 2, 2.0, zx, 2, 1 );



var z = zx.get( 3 );

// returns 



var re = real( z );

// returns 14.0



var im = imag( z );

// returns 16.0

```



## Notes



-   If `N <= 0`, both functions return `zx` unchanged.

-   `zdscal()` corresponds to the [BLAS][blas] level 1 function [`zdscal`][zdscal].



## Examples



```javascript

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );

var filledarrayBy = require( '@stdlib/array-filled-by' );

var Complex128 = require( '@stdlib/complex-float64-ctor' );

var zdscal = require( '@stdlib/blas-base-zdscal' );



function rand() {

    return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );

}



var zx = filledarrayBy( 10, 'complex128', rand );

console.log( zx.toString() );



zdscal( zx.length, 2.0, zx, 1 );

console.log( zx.toString() );

```



* * *



## Notice



This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].



#### Community



[![Chat][chat-image]][chat-url]



---



## License



See [LICENSE][stdlib-license].



## Copyright



Copyright © 2016-2025. The Stdlib [Authors][stdlib-authors].



[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-base-zdscal.svg

[npm-url]: https://npmjs.org/package/@stdlib/blas-base-zdscal



[test-image]: https://github.com/stdlib-js/blas-base-zdscal/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/blas-base-zdscal/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-base-zdscal/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-zdscal?branch=main



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[stdlib]: https://github.com/stdlib-js/stdlib



[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors



[umd]: https://github.com/umdjs/umd

[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules



[deno-url]: https://github.com/stdlib-js/blas-base-zdscal/tree/deno

[deno-readme]: https://github.com/stdlib-js/blas-base-zdscal/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/blas-base-zdscal/tree/umd

[umd-readme]: https://github.com/stdlib-js/blas-base-zdscal/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/blas-base-zdscal/tree/esm

[esm-readme]: https://github.com/stdlib-js/blas-base-zdscal/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/blas-base-zdscal/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-base-zdscal/main/LICENSE



[blas]: http://www.netlib.org/blas



[zdscal]: https://www.netlib.org/lapack/explore-html/d2/de8/group__scal_ga40d50a435a5fcf16cf41fa80d746819f.html#ga40d50a435a5fcf16cf41fa80d746819f



[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray



[@stdlib/array/complex128]: https://github.com/stdlib-js/array-complex128