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  2. Index of coincidence - Wikipedia

    en.wikipedia.org/wiki/Index_of_coincidence

    The products n(n − 1) count the number of combinations of n elements taken two at a time. (Actually this counts each pair twice; the extra factors of 2 occur in both numerator and denominator of the formula and thus cancel out.) Each of the n i occurrences of the i-th letter matches each of the remaining n i − 1 occurrences of the same letter.

  3. List of price index formulas - Wikipedia

    en.wikipedia.org/wiki/List_of_price_index_formulas

    The Marshall-Edgeworth index, credited to Marshall (1887) and Edgeworth (1925), [11] is a weighted relative of current period to base period sets of prices. This index uses the arithmetic average of the current and based period quantities for weighting. It is considered a pseudo-superlative formula and is symmetric. [12]

  4. Similarity measure - Wikipedia

    en.wikipedia.org/wiki/Similarity_measure

    In statistics and related fields, a similarity measure or similarity function or similarity metric is a real-valued function that quantifies the similarity between two objects. Although no single definition of a similarity exists, usually such measures are in some sense the inverse of distance metrics : they take on large values for similar ...

  5. Jaccard index - Wikipedia

    en.wikipedia.org/wiki/Jaccard_index

    For example, consider a supermarket with 1000 products and two customers. The basket of the first customer contains salt and pepper and the basket of the second contains salt and sugar. In this scenario, the similarity between the two baskets as measured by the Jaccard index would be 1/3, but the similarity becomes 0.998 using the SMC.

  6. Cosine similarity - Wikipedia

    en.wikipedia.org/wiki/Cosine_similarity

    The normalized angle, referred to as angular distance, between any two vectors and is a formal distance metric and can be calculated from the cosine similarity. [5] The complement of the angular distance metric can then be used to define angular similarity function bounded between 0 and 1, inclusive.

  7. Dice-Sørensen coefficient - Wikipedia

    en.wikipedia.org/wiki/Dice-Sørensen_coefficient

    Sørensen's original formula was intended to be applied to discrete data. Given two sets, X and Y, it is defined as = | | | | + | | where |X| and |Y| are the cardinalities of the two sets (i.e. the number of elements in each set). The Sørensen index equals twice the number of elements common to both sets divided by the sum of the number of ...

  8. Jaro–Winkler distance - Wikipedia

    en.wikipedia.org/wiki/Jaro–Winkler_distance

    The higher the Jaro–Winkler distance for two strings is, the less similar the strings are. The score is normalized such that 0 means an exact match and 1 means there is no similarity. The original paper actually defined the metric in terms of similarity, so the distance is defined as the inversion of that value (distance = 1 − similarity).

  9. Revealed comparative advantage - Wikipedia

    en.wikipedia.org/wiki/Revealed_comparative_advantage

    It most commonly refers to an index, called the Balassa index, introduced by Béla Balassa (1965). [1] In particular, the revealed comparative advantage of country c {\displaystyle c} in product/commodity/good p {\displaystyle p} is defined by: