Dice's coefficient

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我是靠谱客的博主知性宝贝，最近开发中收集的这篇文章主要介绍Dice's coefficient，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

Dice's coefficient (also known as the Dice coefficient) is a similarity measure related to the Jaccard index.

For sets X and Y of keywords used in information retrieval, the coefficient may be defined as:^[1]

$s = /frac{2 | X /cap Y |}{| X | + | Y |}$

When taken as a string similarity measure, the coefficient may be calculated for two strings, x and y using bigrams as follows:^[2]

$s = /frac{2 n_{t}}{n_{x} + n_{y}}$

where $n t$ is the number of character bigrams found in both strings, $n x$ is the number of bigrams in string x and $n y$ is the number of bigrams in string y. For example, to calculate the similarity between:

night

nacht

We would find the set of bigrams in each word:

{ ni, ig, gh, ht}

{ na, ac, ch, ht}

Each set has 4 elements, and the intersection of these two sets has only one element: ht.

Plugging this into the formula, we calculate, $s = (2 * 1) / (4 + 4) = 0.25$

Notes

^ C. J. van Rijsbergen (1979)
^ Kondrak, G. et al. (2003)

References

C. J. van Rijsbergen (1979) Information Retrieval (London: Butterworths)
Kondrak, G., Marcu, D. and Knight, K. (2003) "Cognates Can Improve Statistical Translation Models" in Proceedings of HLT-NAACL 2003: Human Language Technology Conference of the North American Chapter of the Association for Computational Linguistics, pp. 46--48

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