https://github.com/stdlib-js/ndarray-base-strides2offset
Determine the index offset which specifies the location of the first indexed value in a multidimensional array based on a stride array.
https://github.com/stdlib-js/ndarray-base-strides2offset
array base javascript multidimensional ndarray node node-js nodejs offset shape stdlib strides types util utilities utility utils
Last synced: 2 months ago
JSON representation
Determine the index offset which specifies the location of the first indexed value in a multidimensional array based on a stride array.
- Host: GitHub
- URL: https://github.com/stdlib-js/ndarray-base-strides2offset
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T13:21:29.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2025-07-21T00:56:21.000Z (5 months ago)
- Last Synced: 2025-09-08T12:02:32.507Z (4 months ago)
- Topics: array, base, javascript, multidimensional, ndarray, node, node-js, nodejs, offset, shape, stdlib, strides, types, util, utilities, utility, utils
- Language: C
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 359 KB
- Stars: 2
- 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
- Notice: NOTICE
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README
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# strides2offset
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Determine the index offset which specifies the location of the first indexed value in a multidimensional array based on a stride array.
## Installation
```bash
npm install @stdlib/ndarray-base-strides2offset
```
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 strides2offset = require( '@stdlib/ndarray-base-strides2offset' );
```
#### strides2offset( shape, strides )
Returns the index offset which specifies the location of the first indexed value in a multidimensional array.
```javascript
var offset = strides2offset( [ 3, 2 ], [ 2, 1 ] );
// returns 0
offset = strides2offset( [ 3, 2 ], [ -2, 1 ] );
// returns 4
```
## Examples
```javascript
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var shape2strides = require( '@stdlib/ndarray-base-shape2strides' );
var numel = require( '@stdlib/ndarray-base-numel' );
var randu = require( '@stdlib/random-base-randu' );
var strides2offset = require( '@stdlib/ndarray-base-strides2offset' );
var strides;
var offset;
var shape;
var len;
var arr;
var i;
var j;
shape = [ 0, 0, 0 ];
shape[ 0 ] = discreteUniform( 1, 10 );
shape[ 1 ] = discreteUniform( 1, 10 );
shape[ 2 ] = discreteUniform( 1, 10 );
strides = shape2strides( shape, 'row-major' );
len = numel( shape );
arr = [];
for ( i = 0; i < len; i++ ) {
arr.push( i );
}
for ( i = 0; i < 100; i++ ) {
j = discreteUniform( 0, shape.length-1 );
strides[ j ] *= ( randu() < 0.5 ) ? -1 : 1;
offset = strides2offset( shape, strides );
console.log( 'arr[0][0][0] = %d', arr[ offset ] );
}
```
* * *
## 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].
[npm-image]: http://img.shields.io/npm/v/@stdlib/ndarray-base-strides2offset.svg
[npm-url]: https://npmjs.org/package/@stdlib/ndarray-base-strides2offset
[test-image]: https://github.com/stdlib-js/ndarray-base-strides2offset/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/ndarray-base-strides2offset/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/ndarray-base-strides2offset/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/ndarray-base-strides2offset?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-base-strides2offset/tree/deno
[deno-readme]: https://github.com/stdlib-js/ndarray-base-strides2offset/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/ndarray-base-strides2offset/tree/umd
[umd-readme]: https://github.com/stdlib-js/ndarray-base-strides2offset/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/ndarray-base-strides2offset/tree/esm
[esm-readme]: https://github.com/stdlib-js/ndarray-base-strides2offset/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/ndarray-base-strides2offset/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/ndarray-base-strides2offset/main/LICENSE