npm package: @stdlib/slice-base-reduced-dimensions
Description: Return a list of reduced dimensions in an un-normalized multi-slice.
Author: The Stdlib Authors
Latest version: 0.2.3

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# reducedDimensions

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> Return a list of reduced dimensions in an un-normalized [`MultiSlice`][@stdlib/slice/multi] object.

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<section class="intro">

In a multi-axis indexing expression (e.g., '1,:,2,:,0:10:1'), a non-reduced dimension corresponds to a dimension which is retained in the slice result. Only integer indexing expressions (e.g., only the first and third dimensions in '1,:,2,:,0:10:1') result in dimension reduction; slices always retain respective dimensions, even if a slice is empty or only selects a single element.

</section>

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<section class="installation">

## Installation

```bash
npm install @stdlib/slice-base-reduced-dimensions
```

</section>

<section class="usage">

## Usage

```javascript
var reducedDimensions = require( '@stdlib/slice-base-reduced-dimensions' );
```

<a name="main"></a>

#### reducedDimensions( slice )

Returns a list of reduced dimensions in an un-normalized [`MultiSlice`][@stdlib/slice/multi] object.

```javascript
var MultiSlice = require( '@stdlib/slice-multi' );
var Slice = require( '@stdlib/slice-ctor' );

var s = new MultiSlice( 1, null, 2, void 0, new Slice( 0, 10, 1 ) );
// returns <MultiSlice>

var indices = reducedDimensions( s );
// returns [ 0, 2 ]
```

</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">

</section>

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<!-- Package usage examples. -->

<section class="examples">

## Examples

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

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

```javascript
var S = require( '@stdlib/slice-ctor' );
var MultiSlice = require( '@stdlib/slice-multi' );
var reducedDimensions = require( '@stdlib/slice-base-reduced-dimensions' );

var s = new MultiSlice( null, S(), -1 );
var out = reducedDimensions( s );
console.log( '%s => [%s]', s.toString(), out.join( ',' ) );

s = new MultiSlice( null );
out = reducedDimensions( s );
console.log( '%s => [%s]', s.toString(), out.join( ',' ) );

s = new MultiSlice( S( -1, null, -1 ), 3 );
out = reducedDimensions( s );
console.log( '%s => [%s]', s.toString(), out.join( ',' ) );

s = new MultiSlice( 2, S( -10, -2, 2 ), 3, null );
out = reducedDimensions( s );
console.log( '%s => [%s]', s.toString(), out.join( ',' ) );

s = new MultiSlice( S( 1, 20, 2 ), S( null, null, -1 ) );
out = reducedDimensions( s );
console.log( '%s => [%s]', s.toString(), out.join( ',' ) );
```

</section>

<!-- /.examples -->

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</section>

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* * *

## See Also

-   <span class="package-name">[`@stdlib/slice-base/length`][@stdlib/slice/base/length]</span><span class="delimiter">: </span><span class="description">compute the number of elements in a normalized slice.</span>
-   <span class="package-name">[`@stdlib/slice-base/nonreduced-dimensions`][@stdlib/slice/base/nonreduced-dimensions]</span><span class="delimiter">: </span><span class="description">return a list of non-reduced dimensions in an un-normalized multi-slice.</span>
-   <span class="package-name">[`@stdlib/slice-base/shape`][@stdlib/slice/base/shape]</span><span class="delimiter">: </span><span class="description">compute the shape of a normalized multi-slice.</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

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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

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

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