Dice's Coefficient

Dice's Coefficient(Also known asDICE 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:^[1]

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

WhereNTIs the number of character bigrams found in both strings,NXIs the number of bigrams in stringXAndNYIs the number of bigrams in stringY. For example, to calculate the similarity:

night

nacht

We wocould 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

See also

• Jaccard Index
• Levenshtein distance
• Sø rensen similarity index

Notes

1. ^C. J. van rijsbergen (1979)
2. ^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" inProceedings 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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