expandDimensions

Expand the shape of an array by inserting a new dimension of size one at a specified axis.

Usage

var expandDimensions = require( '@stdlib/ndarray/base/expand-dimensions' );

expandDimensions( x, axis )

Expands the shape of an array x by inserting a new dimension of size one at a specified axis.

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

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

// Prepend a singleton dimension:
var y = expandDimensions( x, 0 );
// returns <ndarray>

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

// Append a singleton dimension:
y = expandDimensions( x, 2 );
// returns <ndarray>

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

// Insert a singleton dimension:
y = expandDimensions( x, 1 );
// returns <ndarray>

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

Notes

A provided axis must reside on the interval [-N-1, N], where N is the rank (i.e., number of dimensions) of the provided input array. If provided a negative axis, the axis position at which to insert a singleton dimension is computed as N + axis + 1. Hence, if provided -1, the resolved axis position is N (i.e., a singleton dimension is appended to the input array).

Examples

var array = require( '@stdlib/ndarray/array' );
var numel = require( '@stdlib/ndarray/base/numel' );
var ind2sub = require( '@stdlib/ndarray/ind2sub' );
var expandDimensions = require( '@stdlib/ndarray/base/expand-dimensions' );

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

// Insert a singleton dimension:
var y = expandDimensions( x, 1 );
// returns <ndarray>

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