sliceDimensionFrom

Return a shifted view of an input ndarray along a specified dimension.

Installation

npm install @stdlib/ndarray-base-slice-dimension-from

Usage

var sliceDimensionFrom = require( '@stdlib/ndarray-base-slice-dimension-from' );

sliceDimensionFrom( x, dim, start, strict, writable )

Returns a shifted view of an input ndarray along a specified dimension.

var ndarray = require( '@stdlib/ndarray-ctor' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );

var buffer = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var shape = [ 3, 2 ];
var strides = [ 2, 1 ];
var offset = 0;

var x = ndarray( 'generic', buffer, shape, strides, offset, 'row-major' );
// returns <ndarray>

var sh = x.shape;
// returns [ 3, 2 ]

var arr = ndarray2array( x );
// returns [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

var y = sliceDimensionFrom( x, 0, 1, false, false );
// returns <ndarray>

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

arr = ndarray2array( y );
// returns [ [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]

The function accepts the following arguments:

• x: input ndarray.
• dim: index of dimension along which to slice. If provided an integer less than zero, the dimension index is resolved relative to the last dimension, with the last dimension corresponding to the value -1.
• start: starting index (inclusive). If provided an integer less than zero, the corresponding element along the specified dimension is resolved relative to the last element along that dimension. For negative integers, the last element corresponds to the value -1.
• strict: boolean indicating whether to enforce strict bounds checking.
• writable: boolean indicating whether a returned ndarray should be writable.

Notes

• The writable parameter only applies to ndarray constructors supporting read-only instances.

Examples

var array = require( '@stdlib/ndarray-array' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var zeroTo = require( '@stdlib/array-base-zero-to' );
var sliceDimensionFrom = require( '@stdlib/ndarray-base-slice-dimension-from' );

// Create a linear ndarray buffer:
var buf = zeroTo( 27 );

// Create an ndarray:
var x = array( buf, {
    'shape': [ 3, 3, 3 ]
});

// Get the last two rows of each matrix:
var y1 = sliceDimensionFrom( x, 1, 1, false, false );
// returns <ndarray>

var a1 = ndarray2array( y1 );
// returns [ [ [ 3, 4, 5 ], [ 6, 7, 8 ] ], [ [ 12, 13, 14 ], [ 15, 16, 17 ] ], [ [ 21, 22, 23 ], [ 24, 25, 26 ] ] ]

// Get the last columns of each matrix:
var y2 = sliceDimensionFrom( x, 2, 1, false, false );
// returns <ndarray>

var a2 = ndarray2array( y2 );
// returns [ [ [ 1, 2 ], [ 4, 5 ], [ 7, 8 ] ], [ [ 10, 11 ], [ 13, 14 ], [ 16, 17 ] ], [ [ 19, 20 ], [ 22, 23 ], [ 25, 26 ] ] ]

// Get the last two matrices:
var y3 = sliceDimensionFrom( x, 0, 1, false, false );
// returns <ndarray>

var a3 = ndarray2array( y3 );
// returns [ [ [ 9, 10, 11 ], [ 12, 13, 14 ], [ 15, 16, 17 ] ], [ [ 18, 19, 20 ], [ 21, 22, 23 ], [ 24, 25, 26 ] ] ]

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.