npm package: @stdlib/array-base-symmetric-filled2d-by
Description: Create a filled two-dimensional symmetric nested array according to a provided callback function.
Author: The Stdlib Authors
Latest version: 0.1.1

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# filled2dBy

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

> Create a filled two-dimensional symmetric nested array according to a provided callback function.

<!-- 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/array-base-symmetric-filled2d-by
```

</section>

<section class="usage">

## Usage

```javascript
var filled2dBy = require( '@stdlib/array-base-symmetric-filled2d-by' );
```

#### filled2dBy( N, clbk\[, thisArg] )

Returns a filled two-dimensional symmetric nested array according to a provided callback function.

```javascript
function clbk( idx ) {
    return idx[ 0 ] + idx[ 1 ];
}

var out = filled2dBy( 2, clbk );
// returns [ [ 0, 1 ], [ 1, 2 ] ]
```

The function accepts the following arguments:

-   **N**: number of rows and columns.
-   **clbk**: callback function.
-   **thisArg**: callback function execution context (_optional_).

When invoked, a callback function is provided a single argument:

-   **indices**: current array element indices.

To set the callback execution context, provide a `thisArg`.

<!-- eslint-disable no-invalid-this -->

```javascript
function clbk() {
    this.count += 1;
    return 1;
}

var ctx = {
    'count': 0
};

var out = filled2dBy( 2, clbk, ctx );
// returns [ [ 1, 1 ], [ 1, 1 ] ];

var cnt = ctx.count;
// returns 3
```

</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

-   As the output array is symmetric, the callback function is only invoked for the elements residing in the upper triangle of the output array (i.e., `indices[1] >= indices[0]`).

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var constantFunction = require( '@stdlib/utils-constant-function' );
var filled2dBy = require( '@stdlib/array-base-symmetric-filled2d-by' );

var out = filled2dBy( 2, constantFunction( 0.0 ) );
// returns [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ]

out = filled2dBy( 2, constantFunction( 'beep' ) );
// returns [ [ 'beep', 'beep' ], [ 'beep', 'beep' ] ]

out = filled2dBy( 2, constantFunction( null ) );
// returns [ [ null, null ], [ null, null ] ]

out = filled2dBy( 2, constantFunction( true ) );
// returns [ [ true, true ], [ true, true ] ]

function clbk( indices ) {
    return indices[ 0 ] + indices[ 1 ];
}
out = filled2dBy( 3, clbk );
// returns [ [ 0, 1, 2 ], [ 1, 2, 3 ], [ 2, 3, 4 ] ]
```

</section>

<!-- /.examples -->

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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].

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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