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https://issues.apache.org/jira/browse/TEXT-155?focusedWorklogId=210235&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-210235
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ASF GitHub Bot logged work on TEXT-155:
---------------------------------------

                Author: ASF GitHub Bot
            Created on: 08/Mar/19 16:48
            Start Date: 08/Mar/19 16:48
    Worklog Time Spent: 10m 
      Work Description: aherbert commented on issue #109: TEXT-155: Add a 
generic IntersectionSimilarity measure
URL: https://github.com/apache/commons-text/pull/109#issuecomment-470996120
 
 
   The new API using `Collection` is done. The class can now support duplicates.
   
   I have added a test to show the class can produce the same result as a case 
insensitive word bigram algorithm documented here: [How to Strike a 
Match](http://www.catalysoft.com/articles/StrikeAMatch.html).
   
   Note: Somewhere between switching computers the git history broke and causes 
a conflict when trying to rebase. It is only 4 files so when finished (merge or 
not) I'll drop the branch and redo with the final files.
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 210235)
    Time Spent: 2h 20m  (was: 2h 10m)

> Add a generic SetSimilarity measure
> -----------------------------------
>
>                 Key: TEXT-155
>                 URL: https://issues.apache.org/jira/browse/TEXT-155
>             Project: Commons Text
>          Issue Type: New Feature
>    Affects Versions: 1.6
>            Reporter: Alex D Herbert
>            Priority: Minor
>          Time Spent: 2h 20m
>  Remaining Estimate: 0h
>
> The {{SimilarityScore<T>}} interface can be used to compute a generic result. 
> I propose to add a class that can compute the intersection between two sets 
> formed from the characters. The sets must be formed from the {{CharSequence}} 
> input to the {{apply}} method using a {{Function<CharSequence, Set<T>>}} to 
> convert the {{CharSequence}}. This function can be passed to the 
> {{SimilarityScore<T>}} during construction.
> The result can then be computed to have the size of each set and the 
> intersection.
> I have created an implementation that can compute the equivalent of the 
> {{JaccardSimilary}} class by creating {{Set<Character>}} and also the 
> F1-score using bigrams (pairs of characters) by creating {{Set<String>}}. 
> This relates to 
> [Text-126|https://issues.apache.org/jira/projects/TEXT/issues/TEXT-126] which 
> suggested an algorithm for the Sorensen-Dice similarity, also known as the 
> F1-score.
> Here is an example:
> {code:java}
> // Match the functionality of the JaccardSimilarity class
> Function<CharSequence, Set<Character>> converter = (cs) -> {
>     final Set<Character> set = new HashSet<>();
>     for (int i = 0; i < cs.length(); i++) {
>         set.add(cs.charAt(i));
>     }
>     return set;
> };
> IntersectionSimilarity<Character> similarity = new 
> IntersectionSimilarity<>(converter);
> IntersectionResult result = similarity.apply("something", "something else");
> {code}
> The result has the size of set A, set B and the intersection between them.
> This class was inspired by my look through the various similarity 
> implementations. All of them except the {{CosineSimilarity}} perform single 
> character matching between the input {{CharSequence}}s. The 
> {{CosineSimilarity}} tokenises using whitespace to create words.
> This more generic type of implementation will allow a user to determine how 
> to divide the {{CharSequence}} but to create the sets that are compared, e.g. 
> single characters, words, bigrams, etc.



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