takeMap

Take elements from an array and return a new array after applying a mapping function.

Installation

npm install @stdlib/array-base-take-map

Usage

var takeMap = require( '@stdlib/array-base-take-map' );

takeMap( x, indices, mode, clbk )

Takes elements from an array and returns a new array after applying a mapping function.

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

function customMapping( value ) {
    return value * 2;
}

var y = takeMap( x, [ 1, 3 ], 'throw', customMapping );
// returns [ 4, 8 ]

The function supports the following parameters:

• x: input array.
• indices: list of indices.
• mode: index mode.
• clbk: function to apply.

takeMap.assign( x, indices, mode, out, stride, offset, clbk )

Takes elements from an array and assigns the values to elements in a provided output array.

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

var out = [ 0, 0, 0, 0, 0, 0 ];
var indices = [ 0, 0, 1, 1, 3, 3 ];

function clbk( val ) {
    return val * 2;
}

var arr = takeMap.assign( x, indices, 'throw', out, -1, out.length-1, clbk );
// returns [ 8, 8, 4, 4, 2, 2 ]

var bool = ( arr === out );
// returns true

The function supports the following parameters:

• x: input array.
• indices: list of indices.
• mode: index mode.
• out: output array.
• stride: output array stride.
• offset: output array offset.
• clbk: callback function.

Examples

var filledBy = require( '@stdlib/array-base-filled-by' );
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var linspace = require( '@stdlib/array-base-linspace' );
var takeMap = require( '@stdlib/array-base-take-map' );

// Generate a linearly spaced array:
var x = linspace( 0, 100, 11 );
console.log( x );

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

// Define a mapping function (e.g., square the value):
function square( val ) {
    return val * val;
}

// Take a random sample of elements from `x` and apply the mapping function:
var y = takeMap( x, indices, 'throw', square );
console.log( y );

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.