broadcastArrayExceptDimensions

Broadcast an input ndarray to a target shape while keeping a list of specified dimensions unchanged.

Installation

npm install @stdlib/ndarray-base-broadcast-array-except-dimensions

Usage

var broadcastArrayExceptDimensions = require( '@stdlib/ndarray-base-broadcast-array-except-dimensions' );

broadcastArrayExceptDimensions( arr, shape, dims )

Broadcasts an input ndarray to a target shape while keeping a list of specified dimensions unchanged.

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

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

// Perform broadcasting:
var y = broadcastArrayExceptDimensions( x, [ 3, 2, 2 ], [ -1 ] );
// returns <ndarray>

var ysh = getShape( y );
// returns [ 3, 2, 2 ]

The function accepts the following arguments:

• arr: input ndarray.
• shape: target shape.
• dims: list of dimensions to exclude from broadcasting. Should be a list of negative integers.

Notes

• The function throws an error if a provided ndarray is incompatible with a provided shape.
• The returned ndarray is a "base" ndarray, and, thus, the returned ndarray 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.
• The function always returns a new ndarray instance even if the input ndarray shape and the desired shape are the same.

Examples

var array = require( '@stdlib/ndarray-array' );
var numel = require( '@stdlib/ndarray-base-numel' );
var ind2sub = require( '@stdlib/ndarray-ind2sub' );
var getShape = require( '@stdlib/ndarray-shape' );
var broadcastArrayExceptDimensions = require( '@stdlib/ndarray-base-broadcast-array-except-dimensions' );

// Create a 1x3 array:
var x = array( [ [ 1, 2, 3 ] ] );
// returns <ndarray>

// Broadcast the array to 2x1x3:
var y = broadcastArrayExceptDimensions( x, [ 2, 2, 3 ], [ -2 ] );
// returns <ndarray>

// Retrieve the shape:
var sh = getShape( y );
// returns [ 2, 1, 3 ]

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

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

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 © 2016-2026. The Stdlib Authors.