npm package: @stdlib/ndarray-base-ind
Description: Return an index given an index mode.
Author: The Stdlib Authors
Latest version: 0.2.3

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# ind

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> Return an index given an index mode.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-base-ind
```

</section>

<section class="usage">

## Usage

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

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

Returns an index given an index `mode`.

<!-- run throws: true -->

```javascript
var idx = ind( 2, 9, 'throw' );
// returns 2

idx = ind( -1, 9, 'throw' );
// throws <RangeError>

idx = ind( 10, 9, 'throw' );
// throws <RangeError>

// 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.

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## 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`.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```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 );
}
```

</section>

<!-- /.examples -->

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</section>

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<section class="related">

</section>

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<section class="main-repo" >

* * *

## 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 &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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