takeMap

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

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 );