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https://github.com/stdlib-js/ndarray-base-ind

Return an index given an index mode.
https://github.com/stdlib-js/ndarray-base-ind

array base clamp idx ind index javascript multidimensional ndarray node node-js nodejs stdlib subscript types util utilities utility utils wrap

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Return an index given an index mode.

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README 

        



  

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# ind



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



> Return an index given an index mode.



## Installation



```bash

npm install @stdlib/ndarray-base-ind

```



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 ind = require( '@stdlib/ndarray-base-ind' );

```



#### ind( idx, max, mode )



Returns an index given an index `mode`.



```javascript

var idx = ind( 2, 9, 'throw' );

// returns 2



idx = ind( -1, 9, 'throw' );

// throws 



idx = ind( 10, 9, 'throw' );

// throws 



// Wrapping indices around using modulo arithmetic:

idx = ind( 2, 9, 'wrap' );

// returns 2



idx = ind( 10, 9, 'wrap' );

// returns 0



idx = ind( -1, 9, 'wrap' );

// returns 9



// Clamping indices to first and last indices:

idx = ind( 2, 9, 'clamp' );

// returns 2



idx = ind( 10, 9, 'clamp' );

// returns 9



idx = ind( -1, 9, 'clamp' );

// returns 0



// Normalizing negative indices:

idx = ind( 2, 9, 'normalize' );

// returns 2



idx = ind( -4, 9, 'normalize' );

// returns 6

```



#### ind.factory( mode )



Returns a function for returning an index according to a provided index `mode`.



```javascript

var fcn = ind.factory( 'clamp' );



var idx = fcn( 2, 9 );

// returns 2



idx = fcn( 10, 9 );

// returns 9



idx = fcn( -1, 9 );

// returns 0

```



The function returns a function accepts the following arguments:



-   **index**: input index.

-   **max**: maximum index value.



## Notes



-   Both functions support the following modes:



    -   **throw**: specifies that the function should throw an error when an index is outside the interval `[0, max]`.

    -   **normalize**: specifies that the function should normalize negative indices and throw an error when an index is outside the interval `[-max-1, max]`.

    -   **wrap**: specifies that the function should wrap around an index using modulo arithmetic.

    -   **clamp**: specifies that the function should set an index less than `0` to `0` (minimum index) and set an index greater than `max` to `max`.



## Examples



```javascript

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );

var ind = require( '@stdlib/ndarray-base-ind' );



var modes;

var mode;

var idx;

var out;

var i;



modes = [ 'clamp', 'wrap' ];



for ( i = 0; i < 100; i++ ) {

    idx = discreteUniform( -20, 20 );

    mode = modes[ discreteUniform( 0, modes.length-1 ) ];

    out = ind( idx, 9, mode );

    console.log( '%d => %s(%d,%d) => %d', idx, mode, 0, 9, out );

}

```



* * *



## 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-base-ind.svg

[npm-url]: https://npmjs.org/package/@stdlib/ndarray-base-ind



[test-image]: https://github.com/stdlib-js/ndarray-base-ind/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/ndarray-base-ind/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/ndarray-base-ind/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/ndarray-base-ind?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-ind/tree/deno

[deno-readme]: https://github.com/stdlib-js/ndarray-base-ind/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/ndarray-base-ind/tree/umd

[umd-readme]: https://github.com/stdlib-js/ndarray-base-ind/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/ndarray-base-ind/tree/esm

[esm-readme]: https://github.com/stdlib-js/ndarray-base-ind/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/ndarray-base-ind/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/ndarray-base-ind/main/LICENSE