In
mathematics
Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
and
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
, a string metric (also known as a string similarity metric or string distance function) is a
metric
Metric or metrical may refer to:
* Metric system, an internationally adopted decimal system of measurement
* An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement
Mathematics
In mathe ...
that measures
distance
Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
("inverse similarity") between two
text strings for
approximate string matching
In computer science, approximate string matching (often colloquially referred to as fuzzy string searching) is the technique of finding strings that match a pattern approximately (rather than exactly). The problem of approximate string matching ...
or comparison and in
fuzzy string searching. A requirement for a string ''metric'' (e.g. in contrast to
string matching
In computer science, string-searching algorithms, sometimes called string-matching algorithms, are an important class of string algorithms that try to find a place where one or several strings (also called patterns) are found within a larger str ...
) is fulfillment of the
triangle inequality
In mathematics, the triangle inequality states that for any triangle, the sum of the lengths of any two sides must be greater than or equal to the length of the remaining side.
This statement permits the inclusion of degenerate triangles, but ...
. For example, the strings "Sam" and "Samuel" can be considered to be close. A string metric provides a number indicating an algorithm-specific indication of distance.
The most widely known string metric is a rudimentary one called the
Levenshtein distance (also known as edit distance). It operates between two input strings, returning a number equivalent to the number of substitutions and deletions needed in order to transform one input string into another. Simplistic string metrics such as
Levenshtein distance have expanded to include phonetic,
token
Token may refer to:
Arts, entertainment, and media
* Token, a game piece or counter, used in some games
* The Tokens, a vocal music group
* Tolkien Black, a recurring character on the animated television series ''South Park,'' formerly known a ...
, grammatical and character-based methods of statistical comparisons.
String metrics are used heavily in
information integration and are currently used in areas including
fraud detection
In law, fraud is intentional deception to secure unfair or unlawful gain, or to deprive a victim of a legal right. Fraud can violate civil law (e.g., a fraud victim may sue the fraud perpetrator to avoid the fraud or recover monetary compensa ...
,
fingerprint analysis,
plagiarism detection
Plagiarism detection or content similarity detection is the process of locating instances of plagiarism or copyright infringement within a work or document. The widespread use of computers and the advent of the Internet have made it easier to pla ...
,
ontology merging,
DNA analysis
Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
, RNA analysis,
image analysis
Image analysis or imagery analysis is the extraction of meaningful information from images; mainly from digital images by means of digital image processing techniques. Image analysis tasks can be as simple as reading bar coded tags or as soph ...
, evidence-based
machine learning
Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence.
Machine ...
,
database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases ...
data deduplication
In computing, data deduplication is a technique for eliminating duplicate copies of repeating data. Successful implementation of the technique can improve storage utilization, which may in turn lower capital expenditure by reducing the overall amou ...
,
data mining,
incremental search,
data integration
Data integration involves combining data residing in different sources and providing users with a unified view of them.
This process becomes significant in a variety of situations, which include both commercial (such as when two similar companies ...
, Malware Detection, and semantic
knowledge integration.
List of string metrics
*
Levenshtein distance, or its generalization
edit distance
In computational linguistics and computer science, edit distance is a string metric, i.e. a way of quantifying how dissimilar two strings (e.g., words) are to one another, that is measured by counting the minimum number of operations required to ...
*
Damerau–Levenshtein distance
*
Sørensen–Dice coefficient
*
Block distance or
L1 distance or
City block distance
*
Hamming distance
In information theory, the Hamming distance between two strings of equal length is the number of positions at which the corresponding symbols are different. In other words, it measures the minimum number of ''substitutions'' required to chan ...
*
Jaro–Winkler distance
In computer science and statistics, the Jaro–Winkler distance is a string metric measuring an edit distance between two sequences. It is a variant proposed in 1990 by William E. Winkler of the Jaro distance metric (1989, Matthew A. Jaro).
...
*
Simple matching coefficient (SMC)
*
Jaccard similarity or
Jaccard coefficient or
Tanimoto coefficient
*
Tversky index
*
Overlap coefficient
*
Variational distance[Sam's String Metrics - Computational Linguistics and Phonetics](_blank)
/ref>
* Hellinger distance or Bhattacharyya distance In statistics, the Bhattacharyya distance measures the similarity of two probability distributions. It is closely related to the Bhattacharyya coefficient which is a measure of the amount of overlap between two statistical samples or populations.
...
* Information radius (Jensen–Shannon divergence
In probability theory and statistics, the Jensen– Shannon divergence is a method of measuring the similarity between two probability distributions. It is also known as information radius (IRad) or total divergence to the average. It is based o ...
)
* Skew divergenceKullback–Leibler divergence
In mathematical statistics, the Kullback–Leibler divergence (also called relative entropy and I-divergence), denoted D_\text(P \parallel Q), is a type of statistical distance: a measure of how one probability distribution ''P'' is different fr ...
* Fellegi and Sunters metric (SFS)
Selected string measures examples
References
External links
String Similarity Metrics for Information Integration
A fairly complete overview
Carnegie Mellon University open source library
StringMetric project
a Scala library of string metrics and phonetic algorithms
Natural project
a JavaScript
JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...
natural language processing library which includes implementations of popular string metrics
{{DEFAULTSORT:String Metric
Metrics