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spreadDimensions

Expand the shape of an array to a specified dimensionality by spreading its dimensions to specified dimension indices and inserting dimensions of size one for the remaining dimensions.

Usage

import spreadDimensions from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-spread-dimensions@deno/mod.js';

spreadDimensions( ndims, x, dims )

Expands the shape of an array to a specified dimensionality by spreading its dimensions to specified dimension indices and inserting dimensions of size one for the remaining dimensions.

import ndarray2array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-to-array@deno/mod.js';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@deno/mod.js';

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

// Prepend a singleton dimension:
var y = spreadDimensions( 3, x, [ 1, 2 ] );
// returns <ndarray>

var sh = y.shape;
// returns [ 1, 2, 2 ]

var a = ndarray2array( y );
// returns [ [ [ 1, 2 ], [ 3, 4 ] ] ]

// Append a singleton dimension:
y = spreadDimensions( 3, x, [ 0, 1 ] );
// returns <ndarray>

sh = y.shape;
// returns [ 2, 2, 1 ]

a = ndarray2array( y );
// returns [ [ [ 1 ], [ 2 ] ], [ [ 3 ], [ 4 ] ] ]

// Insert a singleton dimension:
y = spreadDimensions( 3, x, [ 0, 2 ] );
// returns <ndarray>

sh = y.shape;
// returns [ 2, 1, 2 ]

a = ndarray2array( y );
// returns [ [ [ 1, 2 ] ], [ [ 3, 4 ] ] ]

Notes

• Each provided dimension index must reside on the interval [-ndims, ndims-1]. If provided a negative dimension index, the position at which to place a respective dimension is computed as ndims + index.
• Provided dimension indices must resolve to normalized dimension indices arranged in ascending order.

Examples

import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@deno/mod.js';
import numel from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-numel@deno/mod.js';
import ind2sub from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-ind2sub@deno/mod.js';
import spreadDimensions from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-spread-dimensions@deno/mod.js';

// Create a 2-dimensional array:
var x = array( [ [ 1, 2 ], [ 3, 4 ] ], {
    'order': 'column-major'
});
// returns <ndarray>

// Spread dimensions:
var y = spreadDimensions( 5, x, [ 1, 3 ] );
// returns <ndarray>

// Retrieve the shape:
var sh = y.shape;
// returns [ 1, 2, 1, 2, 1 ]

// 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 ) );
}

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Notice

This package is part of stdlib, a standard library 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 © 2016-2025. The Stdlib Authors.