November: Procrastination Month

    count-min-sketch

    0.1.1 • Public • Published

    count-min-sketch

    An implementation of Coromode and Muthukrishnan's Count-Min sketch data structure for JavaScript. The count-min sketch is basically a high powered generalization of the bloom filter. While a bloom filter gives an efficient way to approximate membership of a set, a count-min sketch can give approximate data about the relative frequency of items in the set.

    For more information see the following references:

    Example

    //Import library
    var createCountMinSketch = require("count-min-sketch")
     
    //Create data structure
    var sketch = createCountMinSketch()
     
    //Increment counters
    sketch.update("foo", 1)
    sketch.update(1515, 104)
     
    //Query results
    console.log(sketch.query(1515))  //Prints 104
    console.log(sketch.query("foo")) //Prints 1

    Install

    npm install count-min-sketch
    

    API

    module.exports is a constructor for the data structure, and you import it like so:

    var createCountMinSketch = require("count-min-sketch")

    var sketch = createCountMinSketch(epsilon, probError[, hashFunc])

    Creates a count-min sketch data structure.

    • epsilon is the accuracy of the data structure (ie the size of bins that we are computing frequencies of)

    • probError is the probability of incorrectly computing a value

    • hashFunc(key, hashes) is a hash function for the data structure. (optional) the parameters to this function are as follows:

      • key is the item that is being hashed
      • hashes is an array of k hashes which are required to be pairwise independent.

    Returns A count-min sketch data structure

    sketch.update(key, v)

    Adds v to key

    • key is the item in the table to increment.
    • v is the amount to add to it

    sketch.query(key)

    Returns the frequency of the item key

    • key is the item whose frequency we are counting

    Returns An estimate of the frequency of key

    sketch.toJSON()

    Returns a serializable JSON representation of the table.

    sketch.fromJSON(obj)

    Converts a JSON object into a deserialized sketch. The hash function is reused from the current sketch.

    Note In order for this to be successful both the serialized hash table and the current hash table have to have the same hash function.

    Credits

    (c) 2013 Mikola Lysenko. MIT License

    Keywords

    none

    Install

    npm i count-min-sketch

    DownloadsWeekly Downloads

    8

    Version

    0.1.1

    License

    MIT

    Last publish

    Collaborators

    • mikolalysenko