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take2d

Take elements from a two-dimensional nested array.

Installation

npm install @stdlib/array-base-take2d

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 take2d = require( '@stdlib/array-base-take2d' );

take2d( x, indices, dimension, mode )

Takes elements along a specified dimension from a two-dimensional nested array according to a specified index mode.

var x = [ [ 1, 2 ], [ 3, 4 ] ];
var indices = [ 1, 1, 0, 0, -1, -1 ];

var y = take2d( x, indices, 1, 'normalize' );
// returns [ [ 2, 2, 1, 1, 2, 2 ], [ 4, 4, 3, 3, 4, 4 ] ]

The function accepts the following arguments:

• x: input nested array.
• indices: list of indices.
• dimension: dimension along which to take elements. If provided a negative integer, the dimension is resolved relative to the last dimension, with the last dimension being -1.
• mode: index mode specifying how to handle an index which is out-of-bounds.

If indices is an empty array, the function returns empty arrays along the specified dimension.

var x = [ [ 1, 2 ], [ 3, 4 ] ];

var y = take2d( x, [], 1, 'throw' );
// returns [ [], [] ]

var z = take2d( x, [], 0, 'throw' );
// returns []

Notes

• The function does not deep copy nested array elements.

Examples

var filled2dBy = require( '@stdlib/array-base-filled2d-by' );
var filledBy = require( '@stdlib/array-base-filled-by' );
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var take2d = require( '@stdlib/array-base-take2d' );

// Generate a random array:
var shape = [ 5, 5 ];
var x = filled2dBy( shape, discreteUniform.factory( 0, 100 ) );
console.log( x );

// Generate an array of random indices:
var N = discreteUniform( 5, 15 );
var indices = filledBy( N, discreteUniform.factory( 0, shape[1]-1 ) );
console.log( indices );

// Take a random sample of elements from `x`:
var y = take2d( x, indices, 1, 'throw' );
console.log( y );

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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.