npm package: @stdlib/ndarray-at
Description: Return an ndarray element.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>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.</p>
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</details>

# at

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

> Return an [`ndarray`][@stdlib/ndarray/ctor] element.

<!-- 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-at
```

</section>

<section class="usage">

## Usage

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

#### at( x\[, ...indices] )

Returns an [`ndarray`][@stdlib/ndarray/ctor] element.

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

var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
// returns <ndarray>

var v = at( x, 0, 0 );
// returns 1

v = at( x, 0, 1 );
// returns 2

v = at( x, 1, 0 );
// returns 3

v = at( x, 1, 1 );
// returns 4
```

The function accepts the following arguments:

-   **x**: input [`ndarray`][@stdlib/ndarray/ctor].
-   **indices**: index arguments. The number of index arguments **must** equal the number of dimensions.

</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

-   If provided out-of-bounds indices, the function always returns `undefined`.

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

    var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
    // returns <ndarray>

    var v = at( x, 10, 20 );
    // returns undefined
    ```

-   Negative indices are resolved relative to the last element along the respective dimension, with the last element corresponding to `-1`.

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

    var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
    // returns <ndarray>

    var v = at( x, -1, -1 );
    // returns 4

    v = at( x, -2, -2 );
    // returns 1
    ```

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

<!-- eslint-disable new-cap -->

```javascript
var cartesianProduct = require( '@stdlib/array-cartesian-product' );
var zeroTo = require( '@stdlib/array-zero-to' );
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var array = require( '@stdlib/ndarray-array' );
var at = require( '@stdlib/ndarray-at' );

// Define a two-dimensional array:
var shape = [ 5, 5 ];
var x = array( discreteUniform( 25, -100, 100 ), {
    'shape': shape
});

// Define lists of dimension indices:
var i0 = zeroTo( shape[ 0 ], 'generic' );
var i1 = zeroTo( shape[ 1 ], 'generic' );

// Create a list of index pairs:
var indices = cartesianProduct( i0, i1 );

// Print array contents...
var idx;
var i;
for ( i = 0; i < x.length; i++ ) {
    idx = indices[ i ];
    console.log( 'x[%d,%d] = %d', idx[ 0 ], idx[ 1 ], at( x, idx[ 0 ], idx[ 1 ] ) );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

<!-- /.references -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/ndarray-array`][@stdlib/ndarray/array]</span><span class="delimiter">: </span><span class="description">multidimensional arrays.</span>
-   <span class="package-name">[`@stdlib/ndarray-slice`][@stdlib/ndarray/slice]</span><span class="delimiter">: </span><span class="description">return a read-only view of an input ndarray.</span>

</section>

<!-- /.related -->

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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].

</section>

<!-- /.stdlib -->

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

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[stdlib]: https://github.com/stdlib-js/stdlib

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[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-at/tree/deno
[deno-readme]: https://github.com/stdlib-js/ndarray-at/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/ndarray-at/tree/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/ndarray-at/main/LICENSE

[@stdlib/ndarray/ctor]: https://www.npmjs.com/package/@stdlib/ndarray-ctor

<!-- <related-links> -->

[@stdlib/ndarray/array]: https://www.npmjs.com/package/@stdlib/ndarray-array

[@stdlib/ndarray/slice]: https://www.npmjs.com/package/@stdlib/ndarray-slice

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</section>

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