Class ShingleBased

java.lang.Object
info.debatty.java.stringsimilarity.ShingleBased
Direct Known Subclasses:
Cosine, Jaccard, QGram, SorensenDice
@Immutable public abstract class ShingleBased extends Object
Abstract class for string similarities that rely on set operations (like cosine similarity or jaccard index). k-shingling is the operation of transforming a string (or text document) into a set of n-grams, which can be used to measure the similarity between two strings or documents. Generally speaking, a k-gram is any sequence of k tokens. We use here the definition from Leskovec, Rajaraman & Ullman (2014), "Mining of Massive Datasets", Cambridge University Press: Multiple subsequent spaces are replaced by a single space, and a k-gram is a sequence of k characters. Default value of k is 3. A good rule of thumb is to imagine that there are only 20 characters and estimate the number of k-shingles as 20^k. For small documents like e-mails, k = 5 is a recommended value. For large documents, such as research articles, k = 9 is considered a safe choice.
Author:
Thibault Debatty

  • Constructor Summary

    Constructors
    Constructor
    Description
    ShingleBased(int k)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    final int
    getK()
    Return k, the length of k-shingles (aka n-grams).
    final Map<String,Integer>
    getProfile(String string)
    Compute and return the profile of s, as defined by Ukkonen "Approximate string-matching with q-grams and maximal matches". https://www.cs.helsinki.fi/u/ukkonen/TCS92.pdf The profile is the number of occurrences of k-shingles, and is used to compute q-gram similarity, Jaccard index, etc.

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

  • Method Details

    • getK

      public final int getK()
      Return k, the length of k-shingles (aka n-grams).
      Returns:
      The length of k-shingles.

    • getProfile

      public final Map<String,Integer> getProfile(String string)
      Compute and return the profile of s, as defined by Ukkonen "Approximate string-matching with q-grams and maximal matches". https://www.cs.helsinki.fi/u/ukkonen/TCS92.pdf The profile is the number of occurrences of k-shingles, and is used to compute q-gram similarity, Jaccard index, etc. Pay attention: the memory requirement of the profile can be up to k * size of the string
      Parameters:
      string -
      Returns:
      the profile of this string, as an unmodifiable Map