slice

Return a view of an input ndarray.

Installation

npm install @stdlib/ndarray-base-slice

Usage

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

slice( x, slice, strict, writable )

Returns a view of an input ndarray.

var Slice = require( '@stdlib/slice-ctor' );
var MultiSlice = require( '@stdlib/slice-multi' );
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 s0 = new Slice( null, null, -2 );
var s1 = new Slice( null, null, -1 );
var s = new MultiSlice( s0, s1 );
// returns <MultiSlice>

var y = slice( x, s, false, false );
// returns <ndarray>

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

arr = ndarray2array( y );
// returns [ [ 6.0, 5.0 ], [ 2.0, 1.0 ] ]

The function accepts the following arguments:

• x: input ndarray.
• slice: a MultiSlice instance.
• 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 S = require( '@stdlib/slice-ctor' );
var E = require( '@stdlib/slice-multi' );
var array = require( '@stdlib/ndarray-array' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var zeroTo = require( '@stdlib/array-base-zero-to' );
var slice = require( '@stdlib/ndarray-base-slice' );

// Alias `null` to allow for more compact indexing expressions:
var _ = null;

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

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

// Get each matrix...
var s1 = E( 0, _, _ );
var y1 = slice( x, s1, false, false );
// returns <ndarray>

var a1 = ndarray2array( y1 );
// returns [ [ 0, 1, 2 ], [ 3, 4, 5 ], [ 6, 7, 8 ] ]

var s2 = E( 1, _, _ );
var y2 = slice( x, s2, false, false );
// returns <ndarray>

var a2 = ndarray2array( y2 );
// returns [ [ 9, 10, 11 ], [ 12, 13, 14 ], [ 15, 16, 17 ] ]

var s3 = E( 2, _, _ );
var y3 = slice( x, s3, false, false );
// returns <ndarray>

var a3 = ndarray2array( y3 );
// returns [ [ 18, 19, 20 ], [ 21, 22, 23 ], [ 24, 25, 26 ] ]

// Reverse all elements:
var s = S( _, _, -1 );
var s4 = E( s, s, s );
var y4 = slice( x, s4, false, false );
// returns <ndarray>

var a4 = ndarray2array( y4 );
// returns [...]

// Get the second rows from each matrix:
var s5 = E( _, 1, _ );
var y5 = slice( x, s5, false, false );
// returns <ndarray>

var a5 = ndarray2array( y5 );
// returns [ [ 3, 4, 5 ], [ 12, 13, 14 ], [ 21, 22, 23 ] ]

// Get the second columns from each matrix:
var s6 = E( _, _, 1 );
var y6 = slice( x, s6, false, false );
// returns <ndarray>

var a6 = ndarray2array( y6 );
// returns [ [ 1, 4, 7 ], [ 10, 13, 16 ], [ 19, 22, 25 ] ]

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.