npm package: @stdlib/ndarray-base-broadcast-array-except-dimensions
Description: Broadcast an input ndarray to a target shape while keeping a list of specified dimensions unchanged.
Author: The Stdlib Authors
Latest version: 0.1.1

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# broadcastArrayExceptDimensions

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

> Broadcast an input [ndarray][@stdlib/ndarray/base/ctor] to a target shape while keeping a list of specified dimensions unchanged.

<!-- 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>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-base-broadcast-array-except-dimensions
```

</section>

<section class="usage">

## Usage

<!-- eslint-disable id-length -->

```javascript
var broadcastArrayExceptDimensions = require( '@stdlib/ndarray-base-broadcast-array-except-dimensions' );
```

#### broadcastArrayExceptDimensions( arr, shape, dims )

Broadcasts an input [ndarray][@stdlib/ndarray/base/ctor] to a target shape while keeping a list of specified dimensions unchanged.

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

// Create a 2x2 ndarray:
var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
// returns <ndarray>

// Perform broadcasting:
var y = broadcastArrayExceptDimensions( x, [ 3, 2, 2 ], [ -1 ] );
// returns <ndarray>

var ysh = getShape( y );
// returns [ 3, 2, 2 ]
```

The function accepts the following arguments:

-   **arr**: input ndarray.
-   **shape**: target shape.
-   **dims**: list of dimensions to exclude from broadcasting. Should be a list of negative integers.

</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

-   The function throws an error if a provided [ndarray][@stdlib/ndarray/base/ctor] is [incompatible][@stdlib/ndarray/base/broadcast-shapes] with a provided shape.
-   The returned [ndarray][@stdlib/ndarray/base/ctor] is a "base" [ndarray][@stdlib/ndarray/base/ctor], and, thus, the returned [ndarray][@stdlib/ndarray/base/ctor] does not perform bounds checking or afford any of the guarantees of the non-base [ndarray][@stdlib/ndarray/ctor] constructor. The primary intent of this function is to broadcast an ndarray-like object within internal implementations and to do so with minimal overhead.
-   The function always returns a new [ndarray][@stdlib/ndarray/base/ctor] instance even if the input [ndarray][@stdlib/ndarray/base/ctor] shape and the desired shape are the same.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var array = require( '@stdlib/ndarray-array' );
var numel = require( '@stdlib/ndarray-base-numel' );
var ind2sub = require( '@stdlib/ndarray-ind2sub' );
var getShape = require( '@stdlib/ndarray-shape' );
var broadcastArrayExceptDimensions = require( '@stdlib/ndarray-base-broadcast-array-except-dimensions' );

// Create a 1x3 array:
var x = array( [ [ 1, 2, 3 ] ] );
// returns <ndarray>

// Broadcast the array to 2x1x3:
var y = broadcastArrayExceptDimensions( x, [ 2, 2, 3 ], [ -2 ] );
// returns <ndarray>

// Retrieve the shape:
var sh = getShape( y );
// returns [ 2, 1, 3 ]

// Retrieve the number of elements:
var N = numel( sh );

// Loop through the array elements...
var sub;
var v;
var i;
for ( i = 0; i < N; i++ ) {
    v = y.iget( i );
    sub = ind2sub( sh, i );
    console.log( 'Y[%s] = %d', sub.join( ', ' ), v );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

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* * *

## 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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