@stdlib/utils-map2

Apply a function to elements in two input arrays and assign the results to an output array.

Science Score: 44.0%

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array call element-wise elementwise invoke javascript map matrix ndarray node node-js nodejs stdlib tensor transform util utilities utility utils vector

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Repository

Apply a function to elements in two input arrays and assign the results to an output array.

Basic Info

Host: GitHub
Owner: stdlib-js
License: apache-2.0
Language: JavaScript
Default Branch: main
Homepage: https://github.com/stdlib-js/stdlib
Size: 3.03 MB

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Stars: 2
Watchers: 3
Forks: 0
Open Issues: 0
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array call element-wise elementwise invoke javascript map matrix ndarray node node-js nodejs stdlib tensor transform util utilities utility utils vector

Created about 4 years ago · Last pushed 11 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!

map2

Apply a function to elements in two input arrays and assign the results to an output array.

## Installation ```bash npm install @stdlib/utils-map2 ``` 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 map2 = require( '@stdlib/utils-map2' ); ``` #### map2( x, y, fcn\[, thisArg] ) Applies a function to elements in two input arrays and assigns the results to a new array. ```javascript var naryFunction = require( '@stdlib/utils-nary-function' ); var add = require( '@stdlib/number-float64-base-add' ); var x = [ 1, 2, 3, 4, 5, 6 ]; var y = [ 1, 1, 1, 1, 1, 1 ]; var out = map2( x, y, naryFunction( add, 2 ) ); // returns [ 2, 3, 4, 5, 6, 7 ] ``` The function accepts both array-like objects and [`ndarray`][@stdlib/ndarray/ctor]-like objects. ```javascript var naryFunction = require( '@stdlib/utils-nary-function' ); var add = require( '@stdlib/number-float64-base-add' ); var array = require( '@stdlib/ndarray-array' ); var opts = { 'dtype': 'generic' }; var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts ); var y = array( [ [ 1, 1, 1 ], [ 1, 1, 1 ] ], opts ); var out = map2( x, y, naryFunction( add, 2 ) ); // returns var v = out.get( 1, 1 ); // returns 6 ``` The applied function is provided the following arguments: - **v1**: element from first input array. - **v2**: element from second input array. - **idx**: element index. - **arrays**: input arrays. To set the `this` context when invoking the input function, provide a `thisArg`. ```javascript var add = require( '@stdlib/number-float64-base-add' ); function fcn( v1, v2 ) { this.count += 1; return add( v1, v2 ); } var x = [ 1, 2, 3, 4, 5, 6 ]; var y = [ 1, 1, 1, 1, 1, 1 ]; var ctx = { 'count': 0 }; var out = map2( x, y, fcn, ctx ); // returns [ 2, 3, 4, 5, 6, 7 ] var cnt = ctx.count; // returns 6 ``` #### map2.assign( x, y, out, fcn\[, thisArg] ) Applies a function to elements in two input arrays and assigns the results to an output array `out`. ```javascript var naryFunction = require( '@stdlib/utils-nary-function' ); var add = require( '@stdlib/number-float64-base-add' ); var x = [ 1, 2, 3, 4, 5, 6 ]; var y = [ 1, 1, 1, 1, 1, 1 ]; var out = [ 0, 0, 0, 0, 0, 0 ]; map2.assign( x, y, out, naryFunction( add, 2 ) ); console.log( out ); // => [ 2, 3, 4, 5, 6, 7 ] ``` The method accepts both array-like objects and [`ndarray`][@stdlib/ndarray/ctor]-like objects. ```javascript var naryFunction = require( '@stdlib/utils-nary-function' ); var add = require( '@stdlib/number-float64-base-add' ); var array = require( '@stdlib/ndarray-array' ); var opts = { 'dtype': 'generic', 'shape': [ 2, 3 ] }; var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts ); var y = array( [ [ 1, 1, 1 ], [ 1, 1, 1 ] ], opts ); var out = array( opts ); map2.assign( x, y, out, naryFunction( add, 2 ) ); var v = out.get( 1, 1 ); // returns 6 ``` Input and output arrays must be either all array-like objects or all [`ndarray`][@stdlib/ndarray/ctor]-like objects. If input and output arrays are array-like objects, all arrays **must** have the same number of elements. If input and output arrays are [`ndarray`][@stdlib/ndarray/ctor]-like objects, the arrays **must** be [broadcast compatible][@stdlib/ndarray/base/broadcast-shapes]. To map from one or more input [`ndarrays`][@stdlib/ndarray/ctor] to an output [`ndarray`][@stdlib/ndarray/ctor] which has the same rank (i.e., dimensionality) and the same number of elements, but which is not [broadcast compatible][@stdlib/ndarray/base/broadcast-shapes], reshape the arrays prior to invocation. ```javascript var naryFunction = require( '@stdlib/utils-nary-function' ); var add = require( '@stdlib/number-float64-base-add' ); var array = require( '@stdlib/ndarray-array' ); var opts = { 'dtype': 'generic', 'shape': [ 2, 3 ] }; var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts ); var y = array( [ [ 1, 1, 1 ], [ 1, 1, 1 ] ], opts ); opts = { 'dtype': 'generic', 'shape': [ 2, 2, 3 ] // broadcast compatible shape }; var out = array( opts ); map2.assign( x, y, out, naryFunction( add, 2 ) ); var v = out.get( 0, 1, 1 ); // returns 6 v = out.get( 1, 1, 1 ); // returns 6 ``` In general, avoid providing output [`ndarray`][@stdlib/ndarray/ctor]-like objects which are [non-contiguous][@stdlib/ndarray/base/assert/is-contiguous] views containing one or more elements referring to the **same** memory location. Writing to an overlapping [non-contiguous][@stdlib/ndarray/base/assert/is-contiguous] view is likely to simultaneously affect multiple elements and yield unexpected results. The applied function is provided the same arguments as with [`map2`](#fcn-map2).

## Notes - The [`map2`](#fcn-map2) function **always** returns an output value having a "generic" data type. For example, if provided array-like objects, the function returns a generic `array`. If provided [`ndarrays`][@stdlib/ndarray/ctor], the function returns an [`ndarray`][@stdlib/ndarray/ctor] having a "generic" data type. Accordingly, when provided a typed array, the [`map2`](#fcn-map2) function does **not** return a typed array of the same type. To assign results to a typed array, use the [`map2.assign`](#method-map2-assign) method. - Both [`map2`](#fcn-map2) and [`map2.assign`](#method-map2-assign) accept array-like objects exposing getters and setters for array element access (e.g., [`Complex64Array`][@stdlib/array/complex64], [`Complex128Array`][@stdlib/array/complex128], etc). ```javascript var naryFunction = require( '@stdlib/utils-nary-function' ); var Complex64Array = require( '@stdlib/array-complex64' ); var Complex64 = require( '@stdlib/complex-float32-ctor' ); var realf = require( '@stdlib/complex-float32-real' ); var imagf = require( '@stdlib/complex-float32-imag' ); var add = require( '@stdlib/complex-float32-base-add' ); var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] ); var y = new Complex64Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] ); var z = new Complex64Array( 4 ); map2.assign( x, y, z, naryFunction( add, 2 ) ); var v = z.get( 0 ); var re = realf( v ); // returns 2.0 var im = imagf( v ); // returns 3.0 ``` - When applying a function to [`ndarray`][@stdlib/ndarray/ctor]-like objects, performance will be best for [`ndarray`][@stdlib/ndarray/ctor]-like objects which are single-segment contiguous. For non-contiguous arrays, see [`@stdlib/ndarray-base/binary`][@stdlib/ndarray/base/binary]. - Both [`map2`](#fcn-map2) and [`map2.assign`](#method-map2-assign) do **not** skip `undefined` elements.

## Examples ```javascript var filledarrayBy = require( '@stdlib/array-filled-by' ); var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory; var naryFunction = require( '@stdlib/utils-nary-function' ); var add = require( '@stdlib/number-float64-base-add' ); var array = require( '@stdlib/ndarray-array' ); var map2 = require( '@stdlib/utils-map2' ); function fill( i ) { var rand = discreteUniform( -10*(i+1), 10*(i+1) ); return filledarrayBy( 10, 'generic', rand ); } // Create two-dimensional ndarrays (i.e., matrices): var opts = { 'dtype': 'generic', 'flatten': true }; var x = array( filledarrayBy( 10, opts.dtype, fill ), opts ); var y = array( filledarrayBy( 10, opts.dtype, fill ), opts ); // Create an explicit binary function: var f = naryFunction( add, 2 ); // Compute element-wise sums... var z = map2( x, y, f ); console.log( 'x:' ); console.log( x.data ); console.log( 'y:' ); console.log( y.data ); console.log( 'z:' ); console.log( z.data ); ```

* * * ## 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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Name: stdlib
Login: stdlib-js
Kind: organization

Website: https://stdlib.io
Twitter: stdlibjs
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Standard library for JavaScript.

Citation (CITATION.cff)

cff-version: 1.2.0
title: stdlib
message: >-
  If you use this software, please cite it using the
  metadata from this file.

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/utils-map2

Apply a function to elements in two input arrays and assign the results to an output array.

Homepage: https://stdlib.io
License: Apache-2.0
Latest release: 0.2.1
published almost 2 years ago

Versions: 4
Dependent Packages: 2
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Downloads: 6 Last month

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planeshifter rreusser stdlib-bot kgryte

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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
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@stdlib/array-base-zeros ^0.0.x
@stdlib/assert-is-array-like-object ^0.0.x
@stdlib/assert-is-function ^0.0.x
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@stdlib/ndarray-base-ndarraylike2object ^0.0.x
@stdlib/ndarray-base-vind2bind ^0.0.x
@stdlib/ndarray-zeros ^0.0.x
@stdlib/string-format ^0.0.x
@stdlib/types ^0.0.x
@stdlib/utils-define-nonenumerable-read-only-property ^0.0.x

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@stdlib/utils-map2

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