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

Copy values from x into y.
https://github.com/stdlib-js/blas-base-dcopy

algebra array blas copy cp dcopy double float64 javascript level-1 linear math mathematics ndarray node node-js nodejs stdlib subroutines vector

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Copy values from x into y.

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README 

        



  

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# dcopy



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



> Copy values from `x` into `y`.



## Installation



```bash

npm install @stdlib/blas-base-dcopy

```



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

```



#### dcopy( N, x, strideX, y, strideY )



Copies values from `x` into `y`.



```javascript

var Float64Array = require( '@stdlib/array-float64' );



var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );

var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );



dcopy( x.length, x, 1, y, 1 );

// y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ]

```



The function has the following parameters:



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

-   **x**: input [`Float64Array`][mdn-float64array].

-   **strideX**: index increment for `x`.

-   **y**: output [`Float64Array`][mdn-float64array].

-   **strideY**: index increment for `y`.



The `N` and stride parameters determine how values from `x` are copied into `y`. For example, to copy in reverse order every other value in `x` into the first `N` elements of `y`,



```javascript

var Float64Array = require( '@stdlib/array-float64' );



var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );



dcopy( 3, x, -2, y, 1 );

// y => [ 5.0, 3.0, 1.0, 10.0, 11.0, 12.0 ]

```



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



```javascript

var Float64Array = require( '@stdlib/array-float64' );



// Initial arrays...

var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );



// Create offset views...

var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element



// Copy in reverse order every other value from `x1` into `y1`...

dcopy( 3, x1, -2, y1, 1 );

// y0 => [ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

```



#### dcopy.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )



Copies values from `x` into `y` using alternative indexing semantics.



```javascript

var Float64Array = require( '@stdlib/array-float64' );



var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );

var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );



dcopy.ndarray( x.length, x, 1, 0, y, 1, 0 );

// y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ]

```



The function has the following additional parameters:



-   **offsetX**: starting index for `x`.

-   **offsetY**: starting index for `y`.



While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to copy every other value in `x` starting from the second value into the last `N` elements in `y` where `x[i] = y[n]`, `x[i+2] = y[n-1]`,...,



```javascript

var Float64Array = require( '@stdlib/array-float64' );



var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );



dcopy.ndarray( 3, x, 2, 1, y, -1, y.length-1 );

// y => [ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

```



## Notes



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

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



## Examples



```javascript

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

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



var opts = {

    'dtype': 'float64'

};

var x = discreteUniform( 10, 0, 500, opts );

console.log( x );



var y = discreteUniform( x.length, 0, 255, opts );

console.log( y );



// Copy elements from `x` into `y` starting from the end of `y`:

dcopy( x.length, x, 1, y, -1 );

console.log( y );

```



* * *



## C APIs



### Usage



```c

#include "stdlib/blas/base/dcopy.h"

```



#### c_dcopy( N, \*X, strideX, \*Y, strideY )



Copies values from `X` into `Y`.



```c

const double x[] = { 1.0, 2.0, 3.0, 4.0 };

double y[] = { 0.0, 0.0, 0.0, 0.0 };



c_dcopy( 4, x, 1, y, 1 );

```



The function accepts the following arguments:



-   **N**: `[in] CBLAS_INT` number of indexed elements.

-   **X**: `[in] double*` input array.

-   **strideX**: `[in] CBLAS_INT` index increment for `X`.

-   **Y**: `[out] double*` output array.

-   **strideY**: `[in] CBLAS_INT` index increment for `Y`.



```c

void c_dcopy( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, double *Y, const CBLAS_INT strideY );

```



#### c_dcopy_ndarray( N, \*X, strideX, offsetX, \*Y, strideY, offsetY )



Copies values from `x` into `y` using alternative indexing semantics.



```c

double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };

double y[] = { 0.0, 0.0, 0.0, 0.0, 0.0 };



c_dcopy_ndarray( 3, x, 1, 2, y, 1, 2 );

```



The function accepts the following arguments:



-   **N**: `[in] CBLAS_INT` number of indexed elements.

-   **X**: `[in] double*` input array.

-   **strideX**: `[in] CBLAS_INT` index increment for `X`.

-   **offsetX**: `[in] CBLAS_INT` starting index for `X`.

-   **Y**: `[out] double*` output array.

-   **strideY**: `[in] CBLAS_INT` index increment for `Y`.

-   **offsetY**: `[in] CBLAS_INT` starting index for `Y`.



```c

void c_dcopy_ndarray( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, double *Y, const CBLAS_INT strideY, const CBLAS_INT offsetY );

```



### Examples



```c

#include "stdlib/blas/base/dcopy.h"

#include 



int main( void ) {

    // Create strided arrays:

    const double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };

    double y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };



    // Specify the number of elements:

    const int N = 4;



    // Specify stride lengths:

    const int strideX = 2;

    const int strideY = -2;



    // Copy elements:

    c_dcopy( N, x, strideX, y, strideY );



    // Print the result:

    for ( int i = 0; i < 8; i++ ) {

        printf( "y[ %i ] = %lf\n", i, y[ i ] );

    }



    // Copy elements:

    c_dcopy_ndarray( N, x, strideX, 0, y, strideY, 6 );



    // Print the result:

    for ( int i = 0; i < 8; i++ ) {

        printf( "y[ %i ] = %lf\n", i, y[ i ] );

    }

}

```



* * *



## See Also



-   [`@stdlib/blas-base/dswap`][@stdlib/blas/base/dswap]: interchange two double-precision floating-point vectors.

-   [`@stdlib/blas-base/gcopy`][@stdlib/blas/base/gcopy]: copy values from x into y.

-   [`@stdlib/blas-base/scopy`][@stdlib/blas/base/scopy]: copy values from x into y.



* * *



## 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 © 2016-2024. The Stdlib [Authors][stdlib-authors].



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

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



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

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



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

[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-dcopy?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-dcopy/tree/deno

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

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

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

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

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

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



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



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



[dcopy]: http://www.netlib.org/lapack/explore-html/de/da4/group__double__blas__level1.html



[mdn-float64array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array



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



[@stdlib/blas/base/dswap]: https://github.com/stdlib-js/blas-base-dswap



[@stdlib/blas/base/gcopy]: https://github.com/stdlib-js/blas-base-gcopy



[@stdlib/blas/base/scopy]: https://github.com/stdlib-js/blas-base-scopy