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https://issues.apache.org/jira/browse/TEXT-155?focusedWorklogId=210527&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-210527
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ASF GitHub Bot logged work on TEXT-155:
---------------------------------------
Author: ASF GitHub Bot
Created on: 09/Mar/19 12:21
Start Date: 09/Mar/19 12:21
Worklog Time Spent: 10m
Work Description: aherbert commented on pull request #109: TEXT-155: Add
a generic IntersectionSimilarity measure
URL: https://github.com/apache/commons-text/pull/109#discussion_r263997429
##########
File path:
src/main/java/org/apache/commons/text/similarity/IntersectionResult.java
##########
@@ -0,0 +1,166 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.text.similarity;
+
+import java.util.Objects;
+
+/**
+ * Container class to store the intersection results between two sets.
+ *
+ * <p>Stores the size of set A, set B and the intersection of A and B
(<code>|A ∩ B|</code>).
+ * The result can be used to produce various similarity metrics, for example
the Jaccard index or
+ * Sørensen-Dice coefficient (F1 score).</p>
+ *
+ * <p>This class is immutable.</p>
+ *
+ * @since 1.7
+ * @see <a href="https://en.wikipedia.org/wiki/Jaccard_index";>Jaccard index</a>
+ * @see <a
href="http://en.wikipedia.org/wiki/S%C3%B8rensen%E2%80%93Dice_coefficient";>Sørensen
Dice coefficient</a>
+ * @see <a href="https://en.wikipedia.org/wiki/F1_score";>F1 score</a>
+ */
+public class IntersectionResult {
+ /**
+ * The size of set A.
+ */
+ private final int sizeA;
+ /**
+ * The size of set B.
+ */
+ private final int sizeB;
+ /**
+ * The size of the intersection between set A and B.
+ */
+ private final int intersection;
+
+ /**
+ * Create the results for an intersection between two sets.
+ *
+ * @param sizeA the size of set A ({@code |A|})
+ * @param sizeB the size of set B ({@code |B|})
+ * @param intersection the size of the intersection of A and B (<code>|A
∩ B|</code>)
+ * @throws IllegalArgumentException if the sizes are negative or the
intersection is greater
+ * than the minimum of the two set sizes
+ */
+ public IntersectionResult(final int sizeA, final int sizeB, final int
intersection) {
+ if (sizeA < 0) {
+ throw new IllegalArgumentException("Set size |A| is not positive:
" + sizeA);
+ }
+ if (sizeB < 0) {
+ throw new IllegalArgumentException("Set size |B| is not positive:
" + sizeB);
+ }
+ if (intersection < 0 || intersection > Math.min(sizeA, sizeB)) {
+ throw new IllegalArgumentException("Invalid intersection of |A|
and |B|: " + intersection);
+ }
+ this.sizeA = sizeA;
+ this.sizeB = sizeB;
+ this.intersection = intersection;
+ }
+
+ /**
+ * Get the size of set A.
+ *
+ * @return |A|
+ */
+ public int getSizeA() {
+ return sizeA;
+ }
+
+ /**
+ * Get the size of set B.
+ *
+ * @return |B|
+ */
+ public int getSizeB() {
+ return sizeB;
+ }
+
+ /**
+ * Get the size of the intersection between set A and B.
+ *
+ * @return <code>|A ∩ B|</code>
+ */
+ public int getIntersection() {
+ return intersection;
+ }
+ /**
+ * Get the size of the union between set A and B.
+ *
+ * @return <code>|A ∪ B|</code>
+ */
+ public long getUnion() {
+ return (long) sizeA + sizeB - intersection;
+ }
+
+ /**
+ * Gets the Jaccard index. The Jaccard is the intersection divided by the
union.
+ *
+ * <pre><code>|A ∩ B| / |A ∪ B| </code></pre>
+ *
+ * <p>This implementation defines the result as zero if there is no
intersection,
+ * even when the union is zero to avoid a {@link Double#NaN} result.</p>
+ *
+ * @return the Jaccard index
+ * @see <a href="https://en.wikipedia.org/wiki/Jaccard_index";>Jaccard
index</a>
+ */
+ public double getJaccardIndex() {
+ return intersection == 0 ? 0.0 : (double) intersection / getUnion();
+ }
+
+ /**
+ * Gets the Sørensen-Dice coefficient. The coefficient is twice the
size of the intersection
+ * divided by the size of both sets.
+ *
+ * <pre>
+ * <code>2|A ∩ B| / (|A| + |B|) </code>
+ * </pre>
+ *
+ * <p>This is also known as the F1 score.
Review comment:
Thanks. I also noticed that but had stopped firing up insignificant changes
to GitHub. It is not detected by checkstyle and I ran `mvn javadoc` OK. It
would have to be a JDK < 1.8 to break building the javadoc IIUC.
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Issue Time Tracking
-------------------
Worklog Id: (was: 210527)
Time Spent: 4h (was: 3h 50m)
> 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: 4h
> 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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