https://github.com/parmentf/random-weighted-choice

Node.js module to make a random choice among weighted elements of table.
https://github.com/parmentf/random-weighted-choice

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Node.js module to make a random choice among weighted elements of table.

• Host: GitHub
• URL: https://github.com/parmentf/random-weighted-choice
• Owner: parmentf
• Created: 2012-12-23T14:35:03.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2022-12-06T06:32:59.000Z (over 1 year ago)
• Last Synced: 2024-06-18T15:57:38.492Z (3 days ago)
• Language: JavaScript
• Size: 142 KB
• Stars: 38
• Watchers: 3
• Forks: 4
• Open Issues: 5
• Metadata Files:
  • Readme: README.md

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• awesome-stars - random-weighted-choice

README

        
# Random Weighted Choice

[![Build Status](https://secure.travis-ci.org/parmentf/random-weighted-choice.png?branch=master)](http://travis-ci.org/parmentf/random-weighted-choice)

[![Code Coverage](https://img.shields.io/codecov/c/github/parmentf/random-weighted-choice.svg)](https://codecov.io/github/parmentf/random-weighted-choice)

Node.js module to make a random choice among weighted elements of table.

## Installation

With [npm](http://npmjs.org) do:

```bash

npm install random-weighted-choice

```

## Examples

Although you can add several times the same id

```js

var rwc = require("random-weighted-choice");

var table = [

  { weight: 1, id: "item1" }, // Element 1

  { weight: 1, id: "item2" }, // Element 2

  { weight: 4, id: "item3" }, // Element with a 4 times likelihood

  { weight: 2, id: "item1" }, // Element 1, weight added with 2 => 3

];

var choosenItem = rwc(table);

var choosenUnlikely = rwc(table, 100); // The last shall be first

var choosenDeterministically = rwc(table, 0);

```

It is better to not use the same twice, if you want a temperature other than

the default one (50).

```js

var rwc = require("random-weighted-choice");

var table = [

  { weight: 1, id: "item1" }, // Element 1

  { weight: 1, id: "item2" }, // Element 2

  { weight: 4, id: "item3" }, // Element with a 4 times likelihood

  { weight: 2, id: "item4" }, // Element 4

  { weight: 2, id: "item5" },

];

var choosenItem = rwc(table);

var choosenUnlikely = rwc(table, 100); // The last shall be first

var choosenDeterministically = rwc(table, 0);

```

Without temperature (second parameter) or a 50 value, likelihoods are:

```txt

{ item1: 10%, item2: 10%, item3: 40%, item4: 20%, item5: 20% }

```

With a temperature value of 100:

```txt

{ item1: 30%, item2: 30%, item3: 0%, item4: 20%, item5: 20% }

```

With a temperature value of 0, modified weights are:

```txt

{ item1: 0, item2: 0, item3: 8, item4: 2, item5: 2 }

```

## Usage

### random-weighted-choice(Array table, Number temperature = 50)

Return the `id` of the chosen item from `table`.

The `table` parameter should contain an Array. Each item of that Array must

bean object, with at least `weight` and `id` property.

Weight values are relative to each other. They are integers.

When the sum of the weight values is `null`, `null` is returned (can't choose).

When the Array is empty, `null` is returned.

More explanations on how it works on [Everything2](http://everything2.com/title/Blackboard+temperature).

## Also

-