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https://github.com/stdlib-js/ndarray-numel-dimension
Return the size (i.e., number of elements) of a specified dimension for a provided ndarray.
https://github.com/stdlib-js/ndarray-numel-dimension
array dim dimension javascript len length multidimensional ndarray node node-js nodejs numel shape size stdlib types util utilities utility utils
Last synced: 2 months ago
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Return the size (i.e., number of elements) of a specified dimension for a provided ndarray.
- Host: GitHub
- URL: https://github.com/stdlib-js/ndarray-numel-dimension
- Owner: stdlib-js
- License: apache-2.0
- Created: 2024-01-01T01:50:34.000Z (12 months ago)
- Default Branch: main
- Last Pushed: 2024-10-01T13:12:15.000Z (3 months ago)
- Last Synced: 2024-10-09T19:33:28.324Z (2 months ago)
- Topics: array, dim, dimension, javascript, len, length, multidimensional, ndarray, node, node-js, nodejs, numel, shape, size, stdlib, types, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 350 KB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
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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!
# numelDimension
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Return the size (i.e., number of elements) of a specified dimension for a provided [ndarray][@stdlib/ndarray/ctor].
## Installation
```bash
npm install @stdlib/ndarray-numel-dimension
```
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 numelDimension = require( '@stdlib/ndarray-numel-dimension' );
```
#### numelDimension( x, dim )
Returns the size (i.e., number of elements) of a specified dimension for a provided [ndarray][@stdlib/ndarray/ctor].
```javascript
var zeros = require( '@stdlib/ndarray-zeros' );
var x = zeros( [ 4, 2, 3 ] );
// returns
var d = numelDimension( x, 0 );
// returns 4
```
The function accepts the following arguments:
- **x**: input ndarray.
- **dim**: dimension index. If provided an integer less than zero, the dimension index is resolved relative to the last dimension, with the last dimension corresponding to the value `-1`.
## Notes
- This function is intended as a slight performance optimization over [`@stdlib/ndarray-shape`][@stdlib/ndarray/shape] when **only** a single dimension size is needed. For retrieving multiple dimension sizes, use [`@stdlib/ndarray/shape`][@stdlib/ndarray/shape] directly.
## Examples
```javascript
var zeros = require( '@stdlib/ndarray-zeros' );
var slice = require( '@stdlib/ndarray-slice' );
var E = require( '@stdlib/slice-multi' );
var S = require( '@stdlib/slice-ctor' );
var numelDimension = require( '@stdlib/ndarray-numel-dimension' );
// Create an array:
var x = zeros( [ 10, 10, 10, 10 ] );
// returns
// Define some slices:
var slices = [
// :,:,:,:
E( null, null, null, null ),
// 5:10,4,2:4,::-1
E( S( 5, 10 ), 4, S( 2, 4 ), S( null, null, -1 ) ),
// :,:,2,:
E( null, null, 2, null ),
// 1,2,3,:
E( 1, 2, 3, null ),
// 1,3,::2,4::2
E( 1, 3, S( null, null, 2 ), S( 4, null, 2 ) )
];
// Resolve the size of the first dimension for each slice...
var s;
var i;
for ( i = 0; i < slices.length; i++ ) {
s = slice( x, slices[ i ] );
console.log( '(%s) => %d', s.shape.join( ',' ), numelDimension( s, 0 ) );
}
```
* * *
## See Also
- [`@stdlib/ndarray-array`][@stdlib/ndarray/array]: multidimensional arrays.
- [`@stdlib/ndarray-ctor`][@stdlib/ndarray/ctor]: multidimensional array constructor.
- [`@stdlib/ndarray-numel`][@stdlib/ndarray/numel]: return the number of elements in an ndarray.
* * *
## 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/ndarray-numel-dimension.svg
[npm-url]: https://npmjs.org/package/@stdlib/ndarray-numel-dimension
[test-image]: https://github.com/stdlib-js/ndarray-numel-dimension/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/ndarray-numel-dimension/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/ndarray-numel-dimension/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/ndarray-numel-dimension?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/ndarray-numel-dimension/tree/deno
[deno-readme]: https://github.com/stdlib-js/ndarray-numel-dimension/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/ndarray-numel-dimension/tree/umd
[umd-readme]: https://github.com/stdlib-js/ndarray-numel-dimension/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/ndarray-numel-dimension/tree/esm
[esm-readme]: https://github.com/stdlib-js/ndarray-numel-dimension/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/ndarray-numel-dimension/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/ndarray-numel-dimension/main/LICENSE
[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray-ctor
[@stdlib/ndarray/shape]: https://github.com/stdlib-js/ndarray-shape
[@stdlib/ndarray/array]: https://github.com/stdlib-js/ndarray-array
[@stdlib/ndarray/numel]: https://github.com/stdlib-js/ndarray-numel