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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; } }




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