Jan Martin Keil created TEXT-131:
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Summary: 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
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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