stdlib-js/array-base-broadcast-array

Broadcast an array to a specified shape.

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broadcastArray

Broadcast an array to a specified shape.

Installation

npm install @stdlib/array-base-broadcast-array

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var broadcastArray = require( '@stdlib/array-base-broadcast-array' );

broadcastArray( x, inShape, outShape )

Broadcasts an array to a specified shape.

var x = [ 1, 2 ];

var out = broadcastArray( x, [ 2 ], [ 2, 2 ] );
// returns {...}

var shape = out.shape;
// returns [ 2, 2 ]

var strides = out.strides;
// returns [ 0, 1 ]

var ref = out.ref;
// returns [ 1, 2 ]

var bool = ( x === ref );
// returns true

var data = out.data;
// returns [ [ 1, 2 ] ]

The function returns an object having the following properties:

• ref: reference to the original input array.
• data: broadcasted array.
• shape: broadcasted array shape.
• strides: broadcasted array strides. Strides describe how to iterate over broadcasted array dimensions.

Notes

• The broadcasted array shares the same data as the input array. As more than one element of a broadcasted array may refer to the same memory location, writing to the broadcasted array may affect multiple elements. If you need to write to the broadcasted array, copy the array before performing operations which may mutate elements.
• The function throws an error if a provided input shape is incompatible with a provided output shape.

Examples

var broadcastArray = require( '@stdlib/array-base-broadcast-array' );

// Create a 2x1 array:
var x = [
    [ 1 ],
    [ 2 ]
];

// Broadcast the array to 3x2x4:
var o = broadcastArray( x, [ 2, 1 ], [ 3, 2, 4 ] );
// returns {...}

// Retrieve the shape:
var sh = o.shape;
// returns [ 3, 2, 4 ]

// Retrieve the array "strides":
var st = o.strides;
// returns [...]

// Initialize loop indices:
var i0 = 0;
var i1 = 0;
var i2 = 0;

// Iterate over elements in the broadcasted array...
var i;
var j;
var k;
for ( i = 0; i < sh[ 0 ]; i++ ) {
    i1 = 0;
    for ( j = 0; j < sh[ 1 ]; j++ ) {
        i2 = 0;
        for ( k = 0; k < sh[ 2 ]; k++ ) {
            console.log( 'y[%s] = %d', [ i, j, k ].join( ',' ), o.data[ i0 ][ i1 ][ i2 ] );
            i2 += st[ 2 ];
        }
        i1 += st[ 1 ];
    }
    i0 += st[ 0 ];
}

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Notice

This package is part of 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, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.