ShingleBased (java-string-similarity 2.0.0 API)

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

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`int`	`getK()`	Return k, the length of k-shingles (aka n-grams).
`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".

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - ShingleBased
```
public ShingleBased(int k)
```
    Parameters:
    
    k -
    
    Throws:
    
    IllegalArgumentException - if k is <= 0
- Method Detail
  - 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