npm package: @stdlib/array-place
Description: Replace elements of an array with provided values according to a provided mask array.
Author: The Stdlib Authors
Latest version: 0.1.2

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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</details>

# place

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

> Replace elements of an array with provided values according to a provided mask array.

<section class="installation">

## Installation

```bash
npm install @stdlib/array-place
```

</section>

<section class="usage">

## Usage

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

#### place( x, mask, values\[, options] )

Replaces elements of an array with provided values according to a provided mask array.

```javascript
var x = [ 1, 2, 3, 4 ];

var out = place( x, [ 0, 1, 0, 1 ], [ 20, 40 ] );
// returns [ 1, 20, 3, 40 ]

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

The function supports the following parameters:

-   **x**: input array.
-   **mask**: mask array.
-   **values**: values to set.
-   **options**: function options.

The function supports the following options:

-   **mode**: string specifying behavior when the number of `values` does not equal the number of truthy `mask` values. Default: `'repeat'`.

The function supports the following modes:

-   `'strict'`: specifies that the function must raise an exception when the number of `values` does not **exactly** equal the number of truthy `mask` values.
-   `'non_strict'`: specifies that the function must raise an exception when the function is provided insufficient `values` to satisfy the `mask` array.
-   `'strict_broadcast'`: specifies that the function must broadcast a single-element `values` array and otherwise raise an exception when the number of `values` does not **exactly** equal the number of truthy `mask` values.
-   `'broadcast'`: specifies that the function must broadcast a single-element `values` array and otherwise raise an exception when the function is provided insufficient `values` to satisfy the `mask` array.
-   `'repeat'`: specifies that the function must reuse provided `values` when replacing elements in `x` in order to satisfy the `mask` array.

In broadcasting modes, the function supports broadcasting a `values` array containing a single element against the number of truthy values in the `mask` array.

```javascript
var x = [ 1, 2, 3, 4 ];

var out = place( x, [ 0, 1, 0, 1 ], [ 20 ], {
    'mode': 'strict_broadcast'
});
// returns [ 1, 20, 3, 20 ]

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

In repeat mode, the function supports recycling elements in a `values` array to satisfy the number of truthy values in the `mask` array.

```javascript
var x = [ 1, 2, 3, 4 ];

var out = place( x, [ 1, 1, 0, 1 ], [ 20, 40 ], {
    'mode': 'repeat'
});
// returns [ 20, 40, 3, 20 ]

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

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The function mutates the input array `x`.
-   If a `mask` array element is truthy, the corresponding element in `x` is **replaced**; otherwise, the corresponding element in `x` is "masked" and thus left unchanged.
-   The `values` array must have a [data type][@stdlib/array/dtypes] which can be [safely cast][@stdlib/array/safe-casts] to the input array data type. Floating-point data types (both real and complex) are allowed to downcast to a lower precision data type of the [same kind][@stdlib/array/same-kind-casts] (e.g., element values from a `'float64'` values array can be assigned to corresponding elements in a `'float32'` input array).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var filledBy = require( '@stdlib/array-base-filled-by' );
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var bernoulli = require( '@stdlib/random-base-bernoulli' );
var linspace = require( '@stdlib/array-base-linspace' );
var place = require( '@stdlib/array-place' );

// Generate a linearly spaced array:
var x = linspace( 0, 100, 11 );
console.log( x );

// Generate a random mask array:
var N = discreteUniform( 5, 15 );
var mask = filledBy( N, bernoulli.factory( 0.3 ) );
console.log( mask );

// Generate an array of random values:
var values = filledBy( N, discreteUniform.factory( 1000, 2000 ) );
console.log( values );

// Update a random sample of elements in `x`:
var out = place( x, mask, values );
console.log( out );
```

</section>

<!-- /.examples -->

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

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/array-mskput`][@stdlib/array/mskput]</span><span class="delimiter">: </span><span class="description">replace elements of an array with provided values according to a provided mask array.</span>
-   <span class="package-name">[`@stdlib/array-put`][@stdlib/array/put]</span><span class="delimiter">: </span><span class="description">replace specified elements of an array with provided values.</span>
-   <span class="package-name">[`@stdlib/array-take`][@stdlib/array/take]</span><span class="delimiter">: </span><span class="description">take elements from an array.</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

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

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

</section>

<!-- /.stdlib -->

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[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/array-place/tree/deno
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/array-place/main/LICENSE

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

[@stdlib/array/safe-casts]: https://www.npmjs.com/package/@stdlib/array-safe-casts

[@stdlib/array/same-kind-casts]: https://www.npmjs.com/package/@stdlib/array-same-kind-casts

<!-- <related-links> -->

[@stdlib/array/mskput]: https://www.npmjs.com/package/@stdlib/array-mskput

[@stdlib/array/put]: https://www.npmjs.com/package/@stdlib/array-put

[@stdlib/array/take]: https://www.npmjs.com/package/@stdlib/array-take

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</section>

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