npm package: @stdlib/blas-ext-join
Description: Return an ndarray created by joining elements using a separator along one or more ndarray dimensions.
Author: The Stdlib Authors
Latest version: 0.1.1

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<details>
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</details>

# join

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

> Return an [ndarray][@stdlib/ndarray/ctor] created by joining elements using a separator along one or more [ndarray][@stdlib/ndarray/ctor] dimensions.

<section class="installation">

## Installation

```bash
npm install @stdlib/blas-ext-join
```

</section>

<section class="usage">

## Usage

```javascript
var join = require( '@stdlib/blas-ext-join' );
```

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

Returns an [ndarray][@stdlib/ndarray/ctor] created by joining elements using a separator along one or more [ndarray][@stdlib/ndarray/ctor] dimensions.

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

// Create an input ndarray:
var x = array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
// returns <ndarray>

// Perform operation:
var out = join( x );
// returns <ndarray>[ '1,2,3,4,5,6' ]
```

The function has the following parameters:

-   **x**: input [ndarray][@stdlib/ndarray/ctor].
-   **options**: function options (_optional_).

The function accepts the following options:

-   **sep**: separator. May be either a scalar value or an [ndarray][@stdlib/ndarray/ctor] having a "generic" [data type][@stdlib/ndarray/dtypes]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the complement of the shape defined by `options.dims`. For example, given the input shape `[2, 3, 4]` and `options.dims=[0]`, an [ndarray][@stdlib/ndarray/ctor] separator value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`. Similarly, when performing the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor], an [ndarray][@stdlib/ndarray/ctor] separator value must be a zero-dimensional [ndarray][@stdlib/ndarray/ctor]. Default: `,`.
-   **dims**: list of dimensions over which to perform operation. If not provided, the function performs the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor].
-   **keepdims**: boolean indicating whether the reduced dimensions should be included in the returned [ndarray][@stdlib/ndarray/ctor] as singleton dimensions. Default: `false`.

By default, the function joins [ndarray][@stdlib/ndarray/ctor] elements by using `,` as a separator. To perform the operation with a different separator, provide a `sep` option.

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

var x = array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var out = join( x, {
    'sep': '|'
});
// returns <ndarray>[ '1|2|3|4|5|6' ]
```

By default, the function performs the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor]. To perform the operation over specific dimensions, provide a `dims` option.

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

var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );

var out = join( x, {
    'dims': [ 0 ]
});
// returns <ndarray>[ '1,3', '2,4' ]

out = join( x, {
    'dims': [ 1 ]
});
// returns <ndarray>[ '1,2', '3,4' ]

out = join( x, {
    'dims': [ 0, 1 ]
});
// returns <ndarray>[ '1,2,3,4' ]
```

By default, the function excludes reduced dimensions from the output [ndarray][@stdlib/ndarray/ctor]. To include the reduced dimensions as singleton dimensions, set the `keepdims` option to `true`.

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

var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );

var opts = {
    'dims': [ 0 ],
    'keepdims': true
};

var out = join( x, opts );
// returns <ndarray>[ [ '1,3', '2,4' ] ]
```

#### join.assign( x, out\[, options] )

Joins elements of an input [ndarray][@stdlib/ndarray/ctor] using a separator along one or more [ndarray][@stdlib/ndarray/ctor] dimensions and assigns results to a provided output [ndarray][@stdlib/ndarray/ctor].

```javascript
var array = require( '@stdlib/ndarray-array' );
var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );

var x = array( [ 1.0, 2.0, 3.0, 4.0 ] );
var y = scalar2ndarray( '', {
    'dtype': 'generic'
});

var out = join.assign( x, y );
// returns <ndarray>[ '1,2,3,4' ]

var bool = ( out === y );
// returns true
```

The method has the following parameters:

-   **x**: input [ndarray][@stdlib/ndarray/ctor].
-   **out**: output [ndarray][@stdlib/ndarray/ctor].
-   **options**: function options (_optional_).

The method accepts the following options:

-   **sep**: separator. May be either a scalar value or an [ndarray][@stdlib/ndarray/ctor] having a "generic" [data type][@stdlib/ndarray/dtypes]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the complement of the shape defined by `options.dims`. For example, given the input shape `[2, 3, 4]` and `options.dims=[0]`, an [ndarray][@stdlib/ndarray/ctor] separator value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`. Similarly, when performing the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor], an [ndarray][@stdlib/ndarray/ctor] separator value must be a zero-dimensional [ndarray][@stdlib/ndarray/ctor]. Default: `,`.
-   **dims**: list of dimensions over which to perform operation. If not provided, the function performs the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor].

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   Setting the `keepdims` option to `true` can be useful when wanting to ensure that the output [ndarray][@stdlib/ndarray/ctor] is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with ndarrays having the same shape as the input [ndarray][@stdlib/ndarray/ctor].

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var ndarray = require( '@stdlib/ndarray-ctor' );
var join = require( '@stdlib/blas-ext-join' );

// Generate an array of random numbers:
var xbuf = discreteUniform( 10, 0, 20, {
    'dtype': 'float64'
});

// Wrap in an ndarray:
var x = new ndarray( 'float64', xbuf, [ 5, 2 ], [ 2, 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );

// Perform operation:
var out = join( x, {
    'dims': [ -1 ]
});

// Print the results:
console.log( ndarray2array( out ) );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</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].

</section>

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[umd]: https://github.com/umdjs/umd
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[deno-url]: https://github.com/stdlib-js/blas-ext-join/tree/deno
[deno-readme]: https://github.com/stdlib-js/blas-ext-join/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/blas-ext-join/tree/umd
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[branches-url]: https://github.com/stdlib-js/blas-ext-join/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ext-join/main/LICENSE

[@stdlib/ndarray/ctor]: https://www.npmjs.com/package/@stdlib/ndarray-ctor

[@stdlib/ndarray/dtypes]: https://www.npmjs.com/package/@stdlib/ndarray-dtypes

[@stdlib/ndarray/base/broadcast-shapes]: https://www.npmjs.com/package/@stdlib/ndarray-base-broadcast-shapes

</section>

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