maybeBroadcastArray

Broadcast an ndarray to a specified shape if and only if the specified shape differs from the provided ndarray's shape.

Installation

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

Usage

var maybeBroadcastArray = require( '@stdlib/ndarray-base-maybe-broadcast-array' );

maybeBroadcastArray( arr, shape )

Broadcasts an ndarray to a specified shape if and only if the specified shape differs from the provided ndarray's shape.

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

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

// Broadcast to a 2x2x2 ndarray:
var y = maybeBroadcastArray( x, [ 2, 2, 2 ] );
// returns <ndarray>

Notes

• The function throws an error if a provided ndarray is incompatible with a provided shape.
• If a provided ndarray has the same shape as the specified shape, the function returns the provided ndarray.
• If a provided ndarray has a different (broadcast compatible) shape than the specified shape, the function returns a new (base) ndarray view of the provided ndarray's data. The view is typically not contiguous. As more than one element of a returned view may refer to the same memory location, writing to the view may affect multiple elements. If you need to write to the returned ndarray, copy the ndarray before performing operations which may mutate elements.
• A returned ndarray is a "base" ndarray, and, thus, a returned ndarray view does not perform bounds checking or afford any of the guarantees of the non-base ndarray constructor. The primary intent of this function is to broadcast an ndarray-like object within internal implementations and to do so with minimal overhead.

Examples

var array = require( '@stdlib/ndarray-array' );
var numel = require( '@stdlib/ndarray-base-numel' );
var ind2sub = require( '@stdlib/ndarray-ind2sub' );
var maybeBroadcastArray = require( '@stdlib/ndarray-base-maybe-broadcast-array' );

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

// Broadcast the array to 3x2x2:
var y = maybeBroadcastArray( x, [ 3, 2, 2 ] );
// returns <ndarray>

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

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

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

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

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.