@stdlib/strided-base-map-by2

Apply a binary function to each pair of elements retrieved from strided input arrays according to a callback function and assign results to a strided output array.

https://github.com/stdlib-js/strided-base-map-by2

Science Score: 44.0%

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accessor apply array base binary callback clbk foreach javascript map ndarray node node-js nodejs stdlib strided transform

Last synced: 4 months ago · JSON representation ·

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Apply a binary function to each pair of elements retrieved from strided input arrays according to a callback function and assign results to a strided output array.

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Host: GitHub
Owner: stdlib-js
License: apache-2.0
Language: JavaScript
Default Branch: main
Homepage: https://github.com/stdlib-js/stdlib
Size: 1.23 MB

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accessor apply array base binary callback clbk foreach javascript map ndarray node node-js nodejs stdlib strided transform

Created about 4 years ago · Last pushed 4 months ago

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Readme Changelog Contributing License Code of conduct Citation Security

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!

mapBy2

Apply a binary function to each pair of elements retrieved from strided input arrays according to a callback function and assign results to a strided output array.

## Installation ```bash npm install @stdlib/strided-base-map-by2 ``` 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 mapBy2 = require( '@stdlib/strided-base-map-by2' ); ``` #### mapBy2( N, x, strideX, y, strideY, z, strideZ, fcn, clbk\[, thisArg] ) Applies a binary function to each pair of elements retrieved from strided input arrays according to a callback function and assigns results to a strided output array. ```javascript var add = require( '@stdlib/number-float64-base-add' ); function accessor( values ) { values[ 0 ] *= 2.0; values[ 1 ] *= 2.0; return values; } var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ]; var y = [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0, 4.0, 4.0 ]; var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]; mapBy2( x.length, x, 1, y, 1, z, 1, add, accessor ); // z => [ -2.0, 4.0, 10.0, -6.0, 14.0, 6.0, 6.0, 2.0 ] ``` 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`. - **fcn**: binary function to apply to callback return values. - **clbk**: callback function which returns an array-like object containing two values. - **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 var add = require( '@stdlib/number-float64-base-add' ); function accessor( values ) { this.count += 1; values[ 0 ] *= 2.0; values[ 1 ] *= 2.0; return values; } var context = { 'count': 0 }; var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ]; var y = [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0, 4.0, 4.0 ]; var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]; mapBy2( x.length, x, 1, y, 1, z, 1, add, accessor, context ); // z => [ -2.0, 4.0, 10.0, -6.0, 14.0, 6.0, 6.0, 2.0 ] var cnt = context.count; // returns 8 ``` 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 var add = require( '@stdlib/number-float64-base-add' ); function accessor( values ) { values[ 0 ] *= 2.0; values[ 1 ] *= 2.0; return values; } var x = [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ]; var y = [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ]; var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]; mapBy2( 3, x, 2, y, -1, z, 1, add, accessor ); // z => [ 2.0, -4.0, -8.0, 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' ); var add = require( '@stdlib/number-float64-base-add' ); function accessor( values ) { values[ 0 ] *= 2.0; values[ 1 ] *= 2.0; return values; } // Initial arrays... var x0 = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] ); var y0 = new Float64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] ); 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*2 ); // start at 3rd element mapBy2( 3, x1, -2, y1, 1, z1, 1, add, accessor ); // z0 => [ 0.0, 0.0, -8.0, -2.0, 2.0, 0.0 ] ``` #### mapBy2.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, z, strideZ, offsetZ, fcn, clbk\[, thisArg] ) Applies a binary function to each pair of elements retrieved from strided input arrays according to a callback function and assigns results to a strided output array using alternative indexing semantics. ```javascript var add = require( '@stdlib/number-float64-base-add' ); function accessor( values ) { values[ 0 ] *= 2.0; values[ 1 ] *= 2.0; return values; } var x = [ -1.0, -2.0, -3.0, -4.0, -5.0 ]; var y = [ 1.0, 1.0, 2.0, 2.0, 3.0 ]; var z = [ 0.0, 0.0, 0.0, 0.0, 0.0 ]; mapBy2.ndarray( x.length, x, 1, 0, y, 1, 0, z, 1, 0, add, accessor ); // z => [ 0.0, -2.0, -2.0, -4.0, -4.0 ] ``` The function accepts the following additional 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` in reverse order, ```javascript var add = require( '@stdlib/number-float64-base-add' ); function accessor( values ) { values[ 0 ] *= 2.0; values[ 1 ] *= 2.0; return values; } var x = [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ]; var y = [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ]; var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]; mapBy2.ndarray( 3, x, 2, 1, y, -1, y.length-1, z, 1, 3, add, accessor ); // z => [ 0.0, 0.0, 0.0, 2.0, -2.0, -8.0 ] ```

## Notes - If a provided callback function does not return any value (or equivalently, explicitly returns `undefined`), the value is **ignored**. ```javascript var add = require( '@stdlib/number-float64-base-add' ); function accessor() { // No-op... } var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ]; var y = [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0, 4.0, 4.0 ]; var z = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]; mapBy2( x.length, x, 1, y, 1, z, 1, add, accessor ); // z => [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] ```

## Examples ```javascript var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory; var filledarray = require( '@stdlib/array-filled' ); var filledarrayBy = require( '@stdlib/array-filled-by' ); var add = require( '@stdlib/number-float64-base-add' ); var mapBy2 = require( '@stdlib/strided-base-map-by2' ); function accessor( values, i ) { if ( (i%3) === 0 ) { // Simulate a "missing" value... return; } return values; } var x = filledarrayBy( 10, 'generic', discreteUniform( -100, 100 ) ); console.log( x ); var y = filledarrayBy( 10, 'generic', discreteUniform( -100, 100 ) ); console.log( y ); var z = filledarray( null, 10, 'generic' ); console.log( z ); mapBy2.ndarray( x.length, x, 1, 0, y, -1, y.length-1, z, 1, 0, add, accessor ); console.log( z ); ```

* * * ## 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].

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Standard library for JavaScript.

Citation (CITATION.cff)

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message: >-
  If you use this software, please cite it using the
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type: software

authors:
  - name: The Stdlib Authors
    url: https://github.com/stdlib-js/stdlib/graphs/contributors

repository-code: https://github.com/stdlib-js/stdlib
url: https://stdlib.io

abstract: |
  Standard library for JavaScript and Node.js.

keywords:
  - JavaScript
  - Node.js
  - TypeScript
  - standard library
  - scientific computing
  - numerical computing
  - statistical computing

license: Apache-2.0 AND BSL-1.0

date-released: 2016

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npmjs.org: @stdlib/strided-base-map-by2

Apply a binary function to each pair of elements retrieved from strided input arrays according to a callback function and assign results to a strided output array.

Homepage: https://stdlib.io
License: Apache-2.0
Latest release: 0.2.2
published over 1 year ago

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@stdlib/bench ^0.0.x development
@stdlib/math-base-assert-is-nan ^0.0.x development
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@stdlib/math-base-special-pow ^0.0.x development
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istanbul ^0.4.1 development
tap-spec 5.x.x development
tape git+https://github.com/kgryte/tape.git#fix/globby development
@stdlib/types ^0.0.x
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@stdlib/strided-base-map-by2

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