mskfilterMap

Apply a mask to a provided input array and return a new array after applying a mapping function.

Installation

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

Usage

var mskfilterMap = require( '@stdlib/array-base-mskfilter-map' );

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

Applies a mask to a provided input array and returns a new array after applying a mapping function.

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

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

var y = mskfilterMap( x, m, clbk );
// returns [ 4, 8 ]

The function supports the following parameters:

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

To set the applied function's execution context, provide a thisArg.

function clbk( x ) {
    this.count += 1;
    return x;
}

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

var ctx = {
    'count': 0
};

var y = mskfilterMap( x, m, clbk, ctx );
// returns [ 1, 2, 4 ]

var v = ctx.count;
// returns 3

The function always returns a new "generic" array.

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

Applies a mask and mapping function to a provided input array and assigns results to elements in a provided output array.

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

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

var out = [ 0, 0, 0, 0 ];
var arr = mskfilterMap.assign( x, m, 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 truthy, the corresponding element in x is included 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 abs2 = require( '@stdlib/math-base-special-abs2' );
var mskfilterMap = require( '@stdlib/array-base-mskfilter-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 );

// Filter an array using the mask:
var y = mskfilterMap( x, mask, abs2 );
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.