mskrejectMap

Apply a mask to a provided input array and map the unmasked values according to a callback function.

Installation

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

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 mskrejectMap = require( '@stdlib/array-base-mskreject-map' );

mskrejectMap( x, mask, clbk[, thisArg ] )

Returns a new array by applying a mask and mapping the unmasked values according to a callback function.

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

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

var y = mskrejectMap( x, [ 0, 1, 0, 1 ], clbk );
// returns [ 2, 6 ]

The function supports the following parameters:

x: input array.
mask: mask array.
clbk: function to apply.
thisArg: applied function execution context (optional).

The clbk function is provided three arguments:

value: current unmasked array element.
index: current unmasked array element index.
arr: input array.

To set the clbk function execution context, provide a thisArg.

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

var mask = [ 0, 1, 0, 1 ];

var increase = 3;

function clbk( value ) {
    return value + this;
}

var out = mskrejectMap( x, mask, clbk, increase );
// returns [ 4, 6 ]

The function always returns a new "generic" array.

mskrejectMap.assign( x, mask, out, stride, offset, clbk[, thisArg ] )

Applies a mask to a provided input array, maps the unmasked values according to a callback function, and assigns to elements in a provided output array.

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

var mask = [ 1, 0, 1, 0 ];

var out = [ 0, 0, 0, 0 ];

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

var arr = mskrejectMap.assign( x, mask, out, -2, out.length-1, clbk );
// returns [ 0, 8, 0, 4 ]

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

The function supports the following parameters:

x: input array.
mask: mask array.
out: output array.
stride: output array stride.
offset: output array offset.
clbk: function to apply.
thisArg: applied function execution context (optional).

Notes

If a mask array element is falsy, the corresponding element in x is mapped in the output array; otherwise, the corresponding element in x is "masked" and thus excluded from the output array.

Examples

var zeroTo = require( '@stdlib/array-base-zero-to' );
var bernoulli = require( '@stdlib/random-array-bernoulli' );
var mskrejectMap = require( '@stdlib/array-base-mskreject-map' );

// Generate a linearly spaced array:
var x = zeroTo( 20 );
console.log( x );

// Generate a random mask:
var mask = bernoulli( x.length, 0.5, {
    'dtype': 'generic'
});
console.log( mask );

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

// Filter an array using the mask:
var y = mskrejectMap( x, mask, clbk );
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.