tverskyIndexOf function

double tverskyIndexOf(String source, String target, { int ngram = 1, double alpha = 0.5, double beta = 0.5, bool ignoreCase = false, bool ignoreWhitespace = false, bool ignoreNumbers = false, bool alphaNumericOnly = false, })

Finds the Tversky similarity index between two strings.

Parameters

• source is the variant string
• target is the prototype string
• alpha is the variant coefficient. Default is 0.5
• beta is the prototype coefficient. Default is 0.5
• if ignoreCase is true, the character case shall be ignored.
• if ignoreWhitespace is true, space, tab, newlines etc whitespace characters will be ignored.
• if ignoreNumbers is true, numbers will be ignored.
• if alphaNumericOnly is true, only letters and digits will be matched.
• ngram is the size a single item group. If n = 1, each individual items are considered separately. If n = 2, two consecutive items are grouped together and treated as one.

TIPS: You can pass both ignoreNumbers and alphaNumericOnly to true to ignore everything else except letters.

Details

Tversky index is an asymmetric similarity measure between sets that compares a variant with a prototype. It is a generalization of the Sørensen–Dice coefficient and Jaccard index.

It may return NaN dependending on the values of alpha and beta.

See Also: tverskyIndex

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Complexity: Time O(n log n) | Space O(n)

Implementation

double tverskyIndexOf(
  String source,
  String target, {
  int ngram = 1,
  double alpha = 0.5,
  double beta = 0.5,
  bool ignoreCase = false,
  bool ignoreWhitespace = false,
  bool ignoreNumbers = false,
  bool alphaNumericOnly = false,
}) {
  source = cleanupString(
    source,
    ignoreCase: ignoreCase,
    ignoreWhitespace: ignoreWhitespace,
    ignoreNumbers: ignoreNumbers,
    alphaNumericOnly: alphaNumericOnly,
  );
  target = cleanupString(
    target,
    ignoreCase: ignoreCase,
    ignoreWhitespace: ignoreWhitespace,
    ignoreNumbers: ignoreNumbers,
    alphaNumericOnly: alphaNumericOnly,
  );
  if (ngram < 2) {
    return tverskyIndex(
      source.codeUnits,
      target.codeUnits,
      alpha: alpha,
      beta: beta,
    );
  } else {
    return tverskyIndex(
      splitStringToSet(source, ngram),
      splitStringToSet(target, ngram),
      alpha: alpha,
      beta: beta,
    );
  }
}