Huge News!Announcing our $40M Series B led by Abstract Ventures.Learn More
Socket
Sign inDemoInstall
Socket

decay

Package Overview
Dependencies
Maintainers
1
Versions
13
Alerts
File Explorer

Advanced tools

Socket logo

Install Socket

Detect and block malicious and high-risk dependencies

Install

decay

Famous sorting algorithms based on vote popularity and time

  • 1.0.12
  • latest
  • Source
  • npm
  • Socket score

Version published
Maintainers
1
Created
Source

decay

npm status build status dependency status coverage status

This library houses 3 popularity estimating algorithms employed by bigger news sites used to sort for best content:

  1. wilsonScore - Reddit's best comment scoring system
  2. redditHot - Reddit's hot post scoring system for news posts
  3. hackerHot - Hackernews' scoring system

Wilson score equation

Algorithms may cause scores to decay based on distance to post time.

1. Decaying algorithms

Algorithms that are designed to decay based on time needs continual recomputation of scores. An example of doing so would be keeping track of, and periodically computing the score(s) required in a node process on a set of suitable candidates:

var decay = require('decay')
  , hotScore = decay.redditHot();

setInterval(function () {
  candidates = []; // perhaps get recent posts saved in db here
  candidates.forEach(function (c) {
    c.score = hotScore(c.upVotes, c.dnVotes, c.date);
    // save so that next GET /entry/ gets an updated ordering
    save(c);
  });
}, 1000 * 60 * 5); // run every 5 minutes, say

2. Non-decaying algorithms

Algorithms that produce a time agnostic popularity score is typically good for comments. For best results, simply recompute the score at every new vote:

var decay = require('decay')
  , wilsonScore = decay.wilsonScore();

// assume req.entry is the item being voted on
app.post('/entry/upvote', middleWare, function (req, res) {
  // call wilsonScore with ups, downs, post_date to recompute
  req.entry.score = wilsonScore(req.entry.upVotes + 1, req.entry.dnVotes, req.entry.postDate);

  // save new score in database so that new pageviews sort
  save(req.entry);
});

Usage

Decay exports 3 scoring function factories.

Two of these algorithms decay with time, and the other is based purely on statistical popularity.

// 1. zero decay
var wilsonScore = decay.wilsonScore(zScore);
var score = wilsonScore(upVotes, downVotes);

// 2. decays
var redditHotScore = decay.redditHot(halflife);
var score = redditHotScore(upVotes, downVotes, date);

// 3. decays
var hackerHotScore = decay.hackerHot(gravity);
var score = hackerHotScore(upVotes, date);

Parameter Explanation

1. Wilson Score

AKA Reddit's Best comment sorting system. Source

Statistically, it is the lower bound of the Wilson Score interval at the alpha level based on supplied Z score.

The optional zScore parameter can be passed as to the exported wilsonScore factory. The Z score is a statistical value which roughly means how many standard deviations of safety you want, so it maps directly onto the confidence level of the Wilson Score interval.

It will default to z=1.96 if left out, representing a 95% confidence level in the lower bound. Otherwise, values through 1.0 (69%), to 3.3 (99.9%) good alternatives.

2. Reddit Hot Sort

Based on the difference between ups/downs, and decays with time. Causes hive mind effects in large crowds.

An optional halflife parameter can be passed to the exported redditHot factory. The half-life defaults to 45000 [s]. For info on the effects on this parameter read the original blog post about it. See also the canonical reddit source version.

3. HackerNews Hot Sort

Based on simply the amount of upvotes, and decays with time. Prone to advertising abuse.

An optional gravity parameter (defaulting to 1.8) can be passed to the exported hackerHot factory. For info on the effects of this parameter read the original blog post about it.

Installation

$ npm install decay

License

MIT-Licensed. See LICENSE file for details.

Keywords

FAQs

Package last updated on 19 Aug 2017

Did you know?

Socket

Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.

Install

Related posts

SocketSocket SOC 2 Logo

Product

  • Package Alerts
  • Integrations
  • Docs
  • Pricing
  • FAQ
  • Roadmap
  • Changelog

Packages

npm

Stay in touch

Get open source security insights delivered straight into your inbox.


  • Terms
  • Privacy
  • Security

Made with ⚡️ by Socket Inc