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About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

groupIndices

NPM version Build Status Coverage Status

Group element indices as arrays associated with distinct keys.

Usage

import groupIndices from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-group-indices@esm/index.mjs';

groupIndices( x, groups )

Groups element indices as arrays associated with distinct keys.

var x = [ 'beep', 'boop', 'foo', 'bar' ];
var groups = [ 'b', 'b', 'f', 'b' ];

var out = groupIndices( x, groups );
// returns { 'b': [ 0, 1, 3 ], 'f': [ 2 ] }

Notes

  • Each value in groups should resolve to a value which can be serialized as an object key. As a counterexample,

    var x = [ 'beep', 'boop', 'foo', 'bar' ];
var groups = [ {}, {}, {}, {} ];

var out = groupIndices( x, groups );
// returns { '[object Object]': [ 0, 1, 2, 3 ] }

    while each "group" is unique, all input array elements resolve to the same group because each group identifier serializes to the same string.

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">

import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@esm/index.mjs';
import take from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-take-indexed@esm/index.mjs';
import groupIndices from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-group-indices@esm/index.mjs';

// Define an initial array of values:
var values = [ 'beep', 'boop', 'foo', 'bar', 'woot', 'woot' ];

// Sample from the initial array to generate a random collection:
var indices = discreteUniform( 100, 0, values.length-1, {
    'dtype': 'generic'
});
var x = take( values, indices );
// returns [...]

// Randomly assign collection values to groups:
var groups = discreteUniform( x.length, 0, values.length, {
    'dtype': 'generic'
});

// Group the values:
var out = groupIndices( x, groups );
// returns {...}

console.log( out );

</script>
</body>
</html>

Notice

This package is part of stdlib, a standard library 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

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.