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# first

> Return a read-only view of the first element (or subarray) along one or more [`ndarray`][@stdlib/ndarray/ctor] dimensions.

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</section>

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<section class="usage">

## Usage

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

#### first( x\[, options] )

Returns a read-only view of the first element (or subarray) along one or more [`ndarray`][@stdlib/ndarray/ctor] dimensions.

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

var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
// returns <ndarray>[ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ]

var v = first( x );
// returns <ndarray>[ 1.0 ]
```

The function accepts the following arguments:

-   **x**: input [`ndarray`][@stdlib/ndarray/ctor].
-   **options**: function options.

The function accepts the following `options`:

-   **dims**: list of dimensions over which to perform the operation. If a dimension index is provided as an integer less than zero, the dimension index is resolved relative to the last dimension, with the last dimension corresponding to the value `-1`. By default, the function performs the operation over all dimensions.

To resolve the first element (or subarray) along one or more specified dimensions, provide a `dims` option:

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

var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
// returns <ndarray>[ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ]

// First column:
var v = first( x, {
    'dims': [ -1 ]
});
// returns <ndarray>[ 1.0, 3.0 ]

// First row:
v = first( x, {
    'dims': [ -2 ]
});
// returns <ndarray>[ 1.0, 2.0 ]
```

</section>

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## Notes

-   The function always returns a **read-only** view. To convert a returned view to a writable [`ndarray`][@stdlib/ndarray/ctor], copy the contents to a new [`ndarray`][@stdlib/ndarray/ctor] (e.g., via [`@stdlib/ndarray/copy`][@stdlib/ndarray/copy]).
-   If provided an empty `dims` array, the function returns a read-only view of the input [`ndarray`][@stdlib/ndarray/ctor].

</section>

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## Examples

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

```javascript
var uniform = require( '@stdlib/random/uniform' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var first = require( '@stdlib/ndarray/first' );

var x = uniform( [ 3, 3, 3 ], -10.0, 10.0 );
console.log( ndarray2array( x ) );

// First scalar element:
var v = first( x );
console.log( v.get() );

// First columns along the innermost dimension:
v = first( x, {
    'dims': [ -1 ]
});
console.log( ndarray2array( v ) );

// First matrix along the outermost dimension:
v = first( x, {
    'dims': [ 0 ]
});
console.log( ndarray2array( v ) );
```

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</section>

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

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

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