https://github.com/stdlib-js/ndarray-slice

Return a read-only view of an input ndarray.
https://github.com/stdlib-js/ndarray-slice
copy data javascript matrix ndarray node node-js nodejs slice stdlib structure types vector view
Last synced: 4 months ago
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Return a read-only view of an input ndarray.
Host: GitHub
URL: https://github.com/stdlib-js/ndarray-slice
Owner: stdlib-js
License: apache-2.0
Created: 2023-09-28T00:52:04.000Z (over 2 years ago)
Default Branch: main
Last Pushed: 2026-03-02T03:18:01.000Z (4 months ago)
Last Synced: 2026-03-02T04:57:52.871Z (4 months ago)
Topics: copy, data, javascript, matrix, ndarray, node, node-js, nodejs, slice, stdlib, structure, types, vector, view
Language: JavaScript
Homepage: https://github.com/stdlib-js/stdlib
Size: 3.73 MB
Stars: 1
Watchers: 2
Forks: 0
Open Issues: 0
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
- Notice: NOTICE
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# slice

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

> Return a read-only view of an input [`ndarray`][@stdlib/ndarray/ctor].

## Installation

```bash

npm install @stdlib/ndarray-slice

```

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 slice = require( '@stdlib/ndarray-slice' );

```

#### slice( x, ...s\[, options] )

Returns a **read-only** view of an input [`ndarray`][@stdlib/ndarray/ctor].

```javascript

var Slice = require( '@stdlib/slice-ctor' );

var MultiSlice = require( '@stdlib/slice-multi' );

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

var ndarray2array = require( '@stdlib/ndarray-to-array' );

var buffer = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];

var shape = [ 3, 2 ];

var strides = [ 2, 1 ];

var offset = 0;

var x = ndarray( 'generic', buffer, shape, strides, offset, 'row-major' );

// returns 

var sh = x.shape;

// returns [ 3, 2 ]

var arr = ndarray2array( x );

// returns [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

var s0 = new Slice( null, null, -2 );

var s1 = new Slice( null, null, -1 );

var s = new MultiSlice( s0, s1 );

// returns 

var y = slice( x, s );

// returns 

sh = y.shape;

// returns [ 2, 2 ]

arr = ndarray2array( y );

// returns [ [ 6.0, 5.0 ], [ 2.0, 1.0 ] ]

```

The function accepts the following arguments:

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

-   **s**: a [`MultiSlice`][@stdlib/slice/multi] instance, an array of slice arguments, or slice arguments as separate arguments.

-   **options**: function options.

The function supports three (mutually exclusive) means for providing slice arguments:

1.  providing a single [`MultiSlice`][@stdlib/slice/multi] instance.

2.  providing a single array of slice arguments.

3.  providing slice arguments as separate arguments.

The following example demonstrates each invocation style returning equivalent results.

```javascript

var Slice = require( '@stdlib/slice-ctor' );

var MultiSlice = require( '@stdlib/slice-multi' );

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

var ndarray2array = require( '@stdlib/ndarray-to-array' );

var buffer = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];

var shape = [ 3, 2 ];

var strides = [ 2, 1 ];

var offset = 0;

var x = ndarray( 'generic', buffer, shape, strides, offset, 'row-major' );

// returns 

var sh = x.shape;

// returns [ 3, 2 ]

var arr = ndarray2array( x );

// returns [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

// 1. Using a MultiSlice:

var s0 = new Slice( 1, null, 1 );

var s1 = new Slice( null, null, 1 );

var s = new MultiSlice( s0, s1 );

// returns 

var y = slice( x, s );

// returns 

sh = y.shape;

// returns [ 2, 2 ]

arr = ndarray2array( y );

// returns [ [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

// 2. Using an array of slice arguments:

y = slice( x, [ s0, s1 ] );

// returns 

sh = y.shape;

// returns [ 2, 2 ]

arr = ndarray2array( y );

// returns [ [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

// 3. Providing separate arguments:

y = slice( x, s0, s1 );

// returns 

sh = y.shape;

// returns [ 2, 2 ]

arr = ndarray2array( y );

// returns [ [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

```

The function supports the following `options`:

-   **strict**: boolean indicating whether to enforce strict bounds checking.

By default, the function throws an error when provided a slice which exceeds array bounds. To return an empty array when a slice exceeds array bounds, set the `strict` option to `false`.

```javascript

var Slice = require( '@stdlib/slice-ctor' );

var MultiSlice = require( '@stdlib/slice-multi' );

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

var ndarray2array = require( '@stdlib/ndarray-to-array' );

var buffer = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];

var shape = [ 3, 2 ];

var strides = [ 2, 1 ];

var offset = 0;

var x = ndarray( 'generic', buffer, shape, strides, offset, 'row-major' );

// returns 

var sh = x.shape;

// returns [ 3, 2 ]

var arr = ndarray2array( x );

// returns [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

var s0 = new Slice( 1, null, 1 );

var s1 = new Slice( 10, 20, 1 );

var s = new MultiSlice( s0, s1 );

// returns 

var y = slice( x, s, {

    'strict': false

});

// returns 

sh = y.shape;

// returns [ 2, 0 ]

arr = ndarray2array( y );

// returns []

```

## Notes

-   A **slice argument** must be either a [`Slice`][@stdlib/slice/ctor], an integer, `null`, or `undefined`.

-   The number of slice dimensions must match the number of array dimensions. Hence, if `x` is a zero-dimensional [`ndarray`][@stdlib/ndarray/ctor], then, if `s` is a [`MultiSlice`][@stdlib/slice/multi], `s` should be empty, and, if `s` is an array, `s` should not contain any slice arguments. Similarly, if `x` is a one-dimensional [`ndarray`][@stdlib/ndarray/ctor], then, if `s` is a [`MultiSlice`][@stdlib/slice/multi], `s` should have one slice dimension, and, if `s` is an array, `s` should contain a single slice argument. And so on and so forth.

## Examples

```javascript

var S = require( '@stdlib/slice-ctor' );

var E = require( '@stdlib/slice-multi' );

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

var ndarray2array = require( '@stdlib/ndarray-to-array' );

var zeroTo = require( '@stdlib/array-base-zero-to' );

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

// Alias `null` to allow for more compact indexing expressions:

var _ = null;

// Create a linear ndarray buffer:

var buf = zeroTo( 27 );

// Create an ndarray:

var x = array( buf, {

    'shape': [ 3, 3, 3 ]

});

// Get each matrix...

var s1 = E( 0, _, _ );

var y1 = slice( x, s1 );

// returns 

var a1 = ndarray2array( y1 );

// returns [ [ 0, 1, 2 ], [ 3, 4, 5 ], [ 6, 7, 8 ] ]

var s2 = E( 1, _, _ );

var y2 = slice( x, s2 );

// returns 

var a2 = ndarray2array( y2 );

// returns [ [ 9, 10, 11 ], [ 12, 13, 14 ], [ 15, 16, 17 ] ]

var s3 = E( 2, _, _ );

var y3 = slice( x, s3 );

// returns 

var a3 = ndarray2array( y3 );

// returns [ [ 18, 19, 20 ], [ 21, 22, 23 ], [ 24, 25, 26 ] ]

// Reverse all elements:

var s = S( _, _, -1 );

var s4 = E( s, s, s );

var y4 = slice( x, s4 );

// returns 

var a4 = ndarray2array( y4 );

// returns [...]

// Get the second rows from each matrix:

var s5 = E( _, 1, _ );

var y5 = slice( x, s5 );

// returns 

var a5 = ndarray2array( y5 );

// returns [ [ 3, 4, 5 ], [ 12, 13, 14 ], [ 21, 22, 23 ] ]

// Get the second columns from each matrix:

var s6 = E( _, _, 1 );

var y6 = slice( x, s6 );

// returns 

var a6 = ndarray2array( y6 );

// returns [ [ 1, 4, 7 ], [ 10, 13, 16 ], [ 19, 22, 25 ] ]

// Use an alternative invocation style:

var y7 = slice( x, _, _, 1 );

// returns 

var a7 = ndarray2array( y7 );

// returns [ [ 1, 4, 7 ], [ 10, 13, 16 ], [ 19, 22, 25 ] ]

// Use an alternative invocation style:

var y8 = slice( x, [ _, _, 1 ] );

// returns 

var a8 = ndarray2array( y8 );

// returns [ [ 1, 4, 7 ], [ 10, 13, 16 ], [ 19, 22, 25 ] ]

```

* * *

## See Also

-   [`@stdlib/ndarray-array`][@stdlib/ndarray/array]: multidimensional arrays.

-   [`@stdlib/ndarray-at`][@stdlib/ndarray/at]: return an ndarray element.

-   [`@stdlib/ndarray-ctor`][@stdlib/ndarray/ctor]: multidimensional array constructor.

-   [`@stdlib/ndarray-slice-assign`][@stdlib/ndarray/slice-assign]: assign element values from a broadcasted input ndarray to corresponding elements in an output ndarray view.

-   [`@stdlib/ndarray-slice-dimension`][@stdlib/ndarray/slice-dimension]: return a read-only view of an input ndarray when sliced along a specified dimension.

* * *

## 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 © 2016-2026. The Stdlib [Authors][stdlib-authors].

[npm-image]: http://img.shields.io/npm/v/@stdlib/ndarray-slice.svg

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

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

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

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

[coverage-url]: https://codecov.io/github/stdlib-js/ndarray-slice?branch=main

[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg

[chat-url]: https://stdlib.zulipchat.com

[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-slice/tree/deno

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

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

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

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

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

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

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

[@stdlib/slice/ctor]: https://github.com/stdlib-js/slice-ctor

[@stdlib/slice/multi]: https://github.com/stdlib-js/slice-multi

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

[@stdlib/ndarray/array]: https://github.com/stdlib-js/ndarray-array

[@stdlib/ndarray/at]: https://github.com/stdlib-js/ndarray-at

[@stdlib/ndarray/slice-assign]: https://github.com/stdlib-js/ndarray-slice-assign

[@stdlib/ndarray/slice-dimension]: https://github.com/stdlib-js/ndarray-slice-dimension
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