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https://issues.apache.org/jira/browse/TEXT-131?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rob Tompkins updated TEXT-131:
------------------------------
Assignee: Rob Tompkins
> JaroWinklerDistance: Calculation deviates from definition
> ---------------------------------------------------------
>
> Key: TEXT-131
> URL: https://issues.apache.org/jira/browse/TEXT-131
> Project: Commons Text
> Issue Type: Bug
> Reporter: Jan Martin Keil
> Assignee: Rob Tompkins
> Priority: Major
>
> The calculation in {{JaroWinklerDistance}} deviates from the definition of
> the Jaro-Winkler Similarity. By definition the common prefix length is only
> determine for the first 4 characters. Further, the JaroWinkler is defined as
> {{JaroSimilarity + ScalingFactor * CommonPrefixLength * (1 - JaroSimilarity
> )}}.
> Therefore, I recommend the following changes:
> # Update Jaro-Winkler Similarity calculation
> {code:java}
> final double jw = j < 0.7D ? j : j + Math.min(defaultScalingFactor, 1D /
> mtp[3]) * mtp[2] * (1D - j);
> {code}
> to
> {code:java}
> final double jw = j < 0.7D ? j : j + defaultScalingFactor * mtp[2] * (1D - j);
> {code}
> # Update calculation of Common Prefix Length
> {code:java}
> for (int mi = 0; mi < min.length(); mi++) {
> {code}
> to
> {code:java}
> for (int mi = 0; mi < Math.min(4, min.length()); mi++) {
> {code}
> # Remove unnecessary return value
> {code:java}
> return new int[] {matches, transpositions, prefix, max.length()};
> {code}
> to
> {code:java}
> return new int[] {matches, transpositions, prefix};
> {code}
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