bifurcate

Split values into two groups.

Usage

var bifurcate = require( '@stdlib/utils/bifurcate' );

bifurcate( collection, [options,] filter )

Splits values into two groups. If an element in filter is truthy, the corresponding element in collection belongs to the first group; otherwise, the collection element belongs to the second group.

var arr = [ 'beep', 'boop', 'foo', 'bar' ];
var filter = [ true, true, false, true ];

var out = bifurcate( arr, filter );
// returns [ [ 'beep', 'boop', 'bar' ], [ 'foo' ] ]

The function accepts the following options:

returns: specifies the output format. If the option equals 'values', the function outputs element values. If the option equals 'indices', the function outputs element indices. If the option equals '*', the function outputs both element indices and values. Default: 'values'.

By default, the function returns element values. To return element indices, set the returns option to 'indices'.

var arr = [ 'beep', 'boop', 'foo', 'bar' ];
var filter = [ true, true, false, true ];

var opts = {
    'returns': 'indices'
};
var out = bifurcate( arr, opts, filter );
// returns [ [ 0, 1, 3 ], [ 2 ] ]

To return index-element pairs, set the returns option to '*'.

var arr = [ 'beep', 'boop', 'foo', 'bar' ];
var filter = [ true, true, false, true ];

var opts = {
    'returns': '*'
};
var out = bifurcate( arr, opts, filter );
// returns [ [ [ 0, 'beep' ], [ 1, 'boop' ], [ 3, 'bar' ] ], [ [ 2, 'foo' ] ] ]

Notes

Both collection and filter must be collections. A collection may be either an Array, Typed Array, or an array-like Object (excluding strings and functions).

Examples

var randu = require( '@stdlib/random/base/randu' );
var floor = require( '@stdlib/math/base/special/floor' );
var bifurcate = require( '@stdlib/utils/bifurcate' );

var vals;
var arr;
var out;
var f;
var i;
var j;

vals = [ 'beep', 'boop', 'foo', 'bar', 'woot', 'woot' ];

// Generate a random collection...
arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
    j = floor( randu()*vals.length );
    arr[ i ] = vals[ j ];
}

// Randomly assign collection values to a group...
f = new Array( arr.length );
for ( i = 0; i < arr.length; i++ ) {
    f[ i ] = ( randu() < 0.5 );
}

// Compute the groups:
out = bifurcate( arr, f );
console.log( out );