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/*
* 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.Map;
/**
* Measures the cosine distance between two character sequences.
*
* It utilizes the {@link CosineSimilarity} to compute the distance. Character sequences
* are converted into vectors through a simple tokenizer that works with a regular expression
* to split words in a sentence.
*
*
* For further explanation about Cosine Similarity and Cosine Distance, refer to
* http://en.wikipedia.org/wiki/Cosine_similarity.
*
*
* @since 1.0
* @see CosineSimilarity
*/
public class CosineDistance implements EditDistance {
/**
* Tokenizer used to convert the character sequence into a vector.
*/
private final Tokenizer tokenizer = new RegexTokenizer();
/**
* Cosine similarity.
*/
private final CosineSimilarity cosineSimilarity = new CosineSimilarity();
@Override
public Double apply(final CharSequence left, final CharSequence right) {
final CharSequence[] leftTokens = tokenizer.tokenize(left);
final CharSequence[] rightTokens = tokenizer.tokenize(right);
final Map leftVector = Counter.of(leftTokens);
final Map rightVector = Counter.of(rightTokens);
final double similarity = cosineSimilarity.cosineSimilarity(leftVector, rightVector);
return 1.0 - similarity;
}
}