Ratio of Relative Frequencies was suggested by Damerau (1993). It considers only the relative frequency of features and relies on the division of the value for the target corpus by the value of the comparison corpus. It can’t deal with words that don’t appear in the comparison corpus.

References

2241481 measure_rrf 1 modern-humanities-research-association 50 date desc 566 https://zeta-project.eu/wp-content/plugins/zotpress/
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Damerau, Fred J., ‘Generating and Evaluating Domain-Oriented Multi-Word Terms from Texts’, Information Processing & Management, 29.4 (1993), pp. 433–47