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# at

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

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</section>

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## 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>

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## 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>

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## 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 ] ) );
}
```

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</section>

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[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray/tree/main/ctor

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