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sliceFrom

Return a shifted view of an input ndarray.

Installation

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

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

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

sliceFrom( x, start, strict, writable )

Returns a shifted view of an input ndarray.

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 s = [ 1, null ];
var y = sliceFrom( x, s, 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.
• start: an array of starting indices (inclusive). Each element must be either null, undefined, or an integer. A value of null or undefined indicates to include all elements along a corresponding dimension. A negative integer indicates to resolve a starting index relative to the last element along a corresponding dimension, with the last element having index -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 sliceFrom = require( '@stdlib/ndarray-base-slice-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 = sliceFrom( x, [ null, 1, null ], 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 two rows and columns of each matrix:
var y2 = sliceFrom( x, [ null, 1, 1 ], false, false );
// returns <ndarray>

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

// Get the last two 2x2 matrices:
var y3 = sliceFrom( x, [ 1, 1, 1 ], false, false );
// returns <ndarray>

var a3 = ndarray2array( y3 );
// returns [ [ [ 13, 14 ], [ 16, 17 ] ], [ [ 22, 23 ], [ 25, 26 ] ] ]

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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

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.