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From Benedikt Ritter <brit...@apache.org>
Subject Re: [text] Initial implementation of the cosine distance for strings (not sequences)
Date Sun, 22 Feb 2015 17:41:45 GMT
Hello Bruno,

2015-02-22 1:22 GMT+01:00 <kinow@apache.org>:

> Repository: commons-text
> Updated Branches:
>   refs/heads/NEW-METRICS 0404dbf4b -> ff1959c84
>
>
> Initial implementation of the cosine distance for strings (not sequences)
>
>
> Project: http://git-wip-us.apache.org/repos/asf/commons-text/repo
> Commit:
> http://git-wip-us.apache.org/repos/asf/commons-text/commit/ff1959c8
> Tree: http://git-wip-us.apache.org/repos/asf/commons-text/tree/ff1959c8
> Diff: http://git-wip-us.apache.org/repos/asf/commons-text/diff/ff1959c8
>
> Branch: refs/heads/NEW-METRICS
> Commit: ff1959c84dce2eac6f2e8432623d2a2a270a5f32
> Parents: 0404dbf
> Author: Bruno P. Kinoshita <kinow@apache.org>
> Authored: Sat Feb 21 22:22:28 2015 -0200
> Committer: Bruno P. Kinoshita <kinow@apache.org>
> Committed: Sat Feb 21 22:22:28 2015 -0200
>
> ----------------------------------------------------------------------
>  .../text/similarity/CosineSimilarity.java       | 48 +++++++++++++++++-
>  .../text/similarity/CosineSimilarityTest.java   | 51 ++++++++++++++++++++
>  2 files changed, 98 insertions(+), 1 deletion(-)
> ----------------------------------------------------------------------
>
>
>
> http://git-wip-us.apache.org/repos/asf/commons-text/blob/ff1959c8/src/main/java/org/apache/commons/text/similarity/CosineSimilarity.java
> ----------------------------------------------------------------------
> diff --git
> a/src/main/java/org/apache/commons/text/similarity/CosineSimilarity.java
> b/src/main/java/org/apache/commons/text/similarity/CosineSimilarity.java
> index 4589c2d..ca9d087 100644
> ---
> a/src/main/java/org/apache/commons/text/similarity/CosineSimilarity.java
> +++
> b/src/main/java/org/apache/commons/text/similarity/CosineSimilarity.java
> @@ -16,6 +16,52 @@
>   */
>  package org.apache.commons.text.similarity;
>
> -public class CosineSimilarity {
> +/**
> + * <p>Measures the Cosine similarity of two CharSequences. It treats the
> CharSequences as
> + * two vectors of an inner product space and compares the angle between
> them.</p>
> + *
> + * <p>
> + * For further explanation about the Cosine Similarity, take a look at its
> + * Wikipedia page at http://en.wikipedia.org/wiki/Cosine_similarity.
> + * </p>
> + *
> + * @since 0.1
> + */
> +public class CosineSimilarity implements StringMetric<Double> {
> +
> +    @Override
> +    public Double compare(CharSequence left, CharSequence right) {
> +        if (left == null || right == null) {
> +            throw new IllegalArgumentException("String parameters must
> not be null");
> +        }
> +        long dotProduct = dot(left, right);
> +        double d1 = 0.0d;
> +        for (int i = 0; i < left.length(); ++i) {
> +            d1 += Math.pow(((int) left.charAt(i)), 2);
> +        }
> +        double d2 = 0.0d;
> +        for (int i = 0; i < right.length(); ++i) {
> +            d2 += Math.pow(((int) right.charAt(i)), 2);
> +        }
> +        double cosineSimilarity = dotProduct / (double) (Math.sqrt(d1) *
> Math.sqrt(d2));
> +        return cosineSimilarity;
> +    }
> +
> +    /**
> +     * Computes the dot product of two CharSequences. It ignores
> remaining characters. It means
> +     * that if a string is longer than other, then a smaller part of it
> will be used to compute
> +     * the dot product.
> +     *
> +     * @param left left string
> +     * @param right right string
> +     * @return the dot product
> +     */
> +    protected long dot(CharSequence left, CharSequence right) {
> +        long dotProduct = 0;
> +        for (int i = 0; i < left.length() && i < right.length(); ++i)
{
> +            dotProduct += (((int) left.charAt(i)) * ((int)
> right.charAt(i)));
> +        }
> +        return dotProduct;
> +    }
>
>  }
>
>
> http://git-wip-us.apache.org/repos/asf/commons-text/blob/ff1959c8/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
> ----------------------------------------------------------------------
> diff --git
> a/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
> b/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
> new file mode 100644
> index 0000000..aa08057
> --- /dev/null
> +++
> b/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
> @@ -0,0 +1,51 @@
> +/*
> + * 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 static org.junit.Assert.assertEquals;
> +
> +import java.math.BigDecimal;
> +import java.math.RoundingMode;
> +
> +import org.junit.BeforeClass;
> +import org.junit.Test;
> +
> +/**
> + * Unit tests for {@link
> org.apache.commons.text.similarity.CosineSimilarity}.
> + */
> +public class CosineSimilarityTest {
> +
> +    private static CosineSimilarity cosineSimilarity;
> +
> +    @BeforeClass
> +    public static void setUp() {
> +        cosineSimilarity = new CosineSimilarity();
> +    }
> +
> +    @Test
> +    public void testCosineSimilarity() {
> +        assertEquals(Double.valueOf(0.62d),
> roundValue(cosineSimilarity.compare("ABCDE", "AB")));
> +        assertEquals(Double.valueOf(1.00d),
> roundValue(cosineSimilarity.compare("AB", "AB")));
>

I don't understand this test case. Why can't we check for the acutal values?


> +    }
> +
> +    // --- Utility methods
> +
> +    private Double roundValue(Double value) {
> +        return (Double) new BigDecimal(value).setScale(2,
> RoundingMode.HALF_UP).doubleValue();
> +    }
> +
> +}
>
>


-- 
http://people.apache.org/~britter/
http://www.systemoutprintln.de/
http://twitter.com/BenediktRitter
http://github.com/britter

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