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https://github.com/stdlib-js/math-strided-ops-add-by

Element-wise addition of two strided arrays via a callback function.
https://github.com/stdlib-js/math-strided-ops-add-by

accessor add addition arithmetic array element-wise javascript map math mathematics ndarray node node-js nodejs stdlib strided sum summation transform vector

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Element-wise addition of two strided arrays via a callback function.

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README 

        



  

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# addBy



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



> Element-wise [addition][@stdlib/math/base/ops/add] of two strided arrays via a callback function.



## Installation



```bash

npm install @stdlib/math-strided-ops-add-by

```



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 addBy = require( '@stdlib/math-strided-ops-add-by' );

```



#### addBy( N, x, strideX, y, strideY, z, strideZ, clbk\[, thisArg] )



Performs element-wise [addition][@stdlib/math/base/ops/add] of two strided arrays via a callback function and assigns each result to an element in an output strided array.



```javascript

function accessor( values ) {

    return values;

}



var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];

var y = [ 11.0, 12.0, 13.0, 14.0, 15.0 ];

var z = [ 0.0, 0.0, 0.0, 0.0, 0.0 ];



addBy( x.length, x, 1, y, 1, z, 1, accessor );

// z => [ 12.0, 14.0, 16.0, 18.0, 20.0 ]

```



The function accepts the following arguments:



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

-   **x**: input [`Array`][mdn-array], [`typed array`][mdn-typed-array], or an array-like object (excluding strings and functions).

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

-   **y**: input [`Array`][mdn-array], [`typed array`][mdn-typed-array], or an array-like object (excluding strings and functions).

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

-   **z**: output [`Array`][mdn-array], [`typed array`][mdn-typed-array], or an array-like object (excluding strings and functions).

-   **strideZ**: index increment for `z`.

-   **clbk**: callback function.

-   **thisArg**: execution context (_optional_).



The invoked callback function is provided four arguments:



-   **values**: input array element values `[vx, vy]`.

-   **idx**: iteration index (zero-based).

-   **indices**: input and output array strided indices `[ix, iy, iz]` (computed according to `offset + idx*stride`).

-   **arrays**: input and output arrays/collections `[x, y, z]`.



To set the callback execution context, provide a `thisArg`.



```javascript

function accessor( values ) {

    this.count += 1;

    return values;

}



var context = {

    'count': 0

};



var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];

var y = [ 11.0, 12.0, 13.0, 14.0, 15.0 ];

var z = [ 0.0, 0.0, 0.0, 0.0, 0.0 ];



addBy( x.length, x, 1, y, 1, z, 1, accessor, context );

// z => [ 12.0, 14.0, 16.0, 18.0, 20.0 ]



var cnt = context.count;

// returns 5

```



The `N` and `stride` parameters determine which elements in the strided arrays are accessed at runtime. For example, to index every other value in `x` and to index the first `N` elements of `y` in reverse order,



```javascript

function accessor( values ) {

    return values;

}



var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];

var y = [ 11.0, 12.0, 13.0, 14.0, 15.0, 16.0 ];

var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];



addBy( 3, x, 2, y, -1, z, 1, accessor );

// z => [ 14.0, 15.0, 16.0, 0.0, 0.0, 0.0 ]

```



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' );



function accessor( values ) {

    return values;

}



// Initial arrays...

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

var y0 = new Float64Array( [ 11.0, 12.0, 13.0, 14.0, 15.0, 16.0 ] );

var z0 = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );



// 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

var z1 = new Float64Array( z0.buffer, z0.BYTES_PER_ELEMENT*3 ); // start at 4th element



addBy( 3, x1, -2, y1, 1, z1, 1, accessor );

// z0 => [ 0.0, 0.0, 0.0, 20.0, 19.0, 18.0 ]

```



#### addBy.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, z, strideZ, offsetZ, clbk\[, thisArg] )



Performs element-wise [addition][@stdlib/math/base/ops/add] of two strided arrays via a callback function and assigns each result to an element in an output strided array using alternative indexing semantics.



```javascript

function accessor( values ) {

    return values;

}



var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];

var y = [ 11.0, 12.0, 13.0, 14.0, 15.0 ];

var z = [ 0.0, 0.0, 0.0, 0.0, 0.0 ];



addBy.ndarray( x.length, x, 1, 0, y, 1, 0, z, 1, 0, accessor );

// z => [ 12.0, 14.0, 16.0, 18.0, 20.0 ]

```



The function accepts the following [addition][@stdlib/math/base/ops/add]al arguments:



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

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

-   **offsetZ**: starting index for `z`.



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 index every other value in `x` starting from the second value and to index the last `N` elements in `y`,



```javascript

function accessor( values ) {

    return values;

}



var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];

var y = [ 11.0, 12.0, 13.0, 14.0, 15.0, 16.0 ];

var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];



addBy.ndarray( 3, x, 2, 1, y, -1, y.length-1, z, 1, 2, accessor );

// z => [ 0.0, 0.0, 0.0, 20.0, 19.0, 18.0 ]

```



## Notes



-   If a provided callback function does not return any value (or equivalently, explicitly returns `undefined`), the value is **ignored**.



    ```javascript

    function accessor() {

        // No-op...

    }



    var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];

    var y = [ 11.0, 12.0, 13.0, 14.0, 15.0 ];

    var z = [ 0.0, 0.0, 0.0, 0.0, 0.0 ];



    addBy( x.length, x, 1, y, 1, z, 1, accessor );

    // z => [ 0.0, 0.0, 0.0, 0.0, 0.0 ]

    ```



## Examples



```javascript

var uniform = require( '@stdlib/random-base-uniform' ).factory;

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

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

var addBy = require( '@stdlib/math-strided-ops-add-by' );



function accessor( values, i ) {

    if ( (i%3) === 0 ) {

        // Simulate a "missing" value...

        return;

    }

    return values;

}



var x = filledarrayBy( 10, 'generic', uniform( -10.0, 10.0 ) );

console.log( x );



var y = filledarrayBy( x.length, 'generic', uniform( -10.0, 10.0 ) );

console.log( y );



var z = filledarray( null, x.length, 'generic' );

console.log( z );



addBy.ndarray( x.length, x, 1, 0, y, -1, y.length-1, z, 1, 0, accessor );

console.log( z );

```



* * *



## See Also



-   [`@stdlib/math-strided/ops/add`][@stdlib/math/strided/ops/add]: element-wise addition of two strided arrays.

-   [`@stdlib/math-strided/ops/mul-by`][@stdlib/math/strided/ops/mul-by]: element-wise multiplication of two strided arrays via a callback function.

-   [`@stdlib/math-strided/ops/sub-by`][@stdlib/math/strided/ops/sub-by]: element-wise subtraction of two strided arrays via a callback function.



* * *



## 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/math-strided-ops-add-by.svg

[npm-url]: https://npmjs.org/package/@stdlib/math-strided-ops-add-by



[test-image]: https://github.com/stdlib-js/math-strided-ops-add-by/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/math-strided-ops-add-by/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/math-strided-ops-add-by/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/math-strided-ops-add-by?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/math-strided-ops-add-by/tree/deno

[deno-readme]: https://github.com/stdlib-js/math-strided-ops-add-by/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/math-strided-ops-add-by/tree/umd

[umd-readme]: https://github.com/stdlib-js/math-strided-ops-add-by/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/math-strided-ops-add-by/tree/esm

[esm-readme]: https://github.com/stdlib-js/math-strided-ops-add-by/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/math-strided-ops-add-by/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-strided-ops-add-by/main/LICENSE



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



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



[@stdlib/math/base/ops/add]: https://github.com/stdlib-js/math-base-ops-add



[@stdlib/math/strided/ops/add]: https://github.com/stdlib-js/math-strided-ops-add



[@stdlib/math/strided/ops/mul-by]: https://github.com/stdlib-js/math-strided-ops-mul-by



[@stdlib/math/strided/ops/sub-by]: https://github.com/stdlib-js/math-strided-ops-sub-by