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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Work logged] (TEXT-155) Add a generic SetSimilarity measure
Date Sat, 09 Mar 2019 12:20:00 GMT

     [ https://issues.apache.org/jira/browse/TEXT-155?focusedWorklogId=210526&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-210526
]

ASF GitHub Bot logged work on TEXT-155:
---------------------------------------

                Author: ASF GitHub Bot
            Created on: 09/Mar/19 12:19
            Start Date: 09/Mar/19 12:19
    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_r263997361
 
 

 ##########
 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
&#8745; B|</code>).
+ * The result can be used to produce various similarity metrics, for example the Jaccard
index or
+ * S&#248;rensen-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">S&#248;rensen
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 &#8745;
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 &#8745; B|</code>
+     */
+    public int getIntersection() {
+        return intersection;
+    }
+    /**
+     * Get the size of the union between set A and B.
+     *
+     * @return <code>|A &#8746; 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 &#8745; B| / |A &#8746; 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();
+    }
 
 Review comment:
   IMO this is the correct thing to do. Make Jaccard use this class.
   
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 210526)
    Time Spent: 3h 50m  (was: 3h 40m)

> 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: 3h 50m
>  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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