mskrejectMap

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

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 );