com.ibm.watson.catalyst.corpus.tfidf.sentences.BigramHashtable.java Source code

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/*******************************************************************************
 * Copyright 2015 IBM Corporation
 *
 * Licensed 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 com.ibm.watson.catalyst.corpus.tfidf.sentences;

import java.util.List;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import com.ibm.watson.catalyst.corpus.tfidf.util.SortedArrayList;

@SuppressWarnings("serial")
public class BigramHashtable extends FrequencyHashtable<Bigram> {

    public Integer put(Bigram b, int aInt) {
        _frequencies.addAll(b.getWords());
        return super.put(b, aInt);
    }

    public Integer put(String aWord1, String aWord2, int aInt) {
        return (put(bigram(aWord1, aWord2), aInt));
    }

    public Integer get(String aWord1, String aWord2) {
        return get(bigram(aWord1, aWord2));
    }

    public Integer add(String aWord1, String aWord2) {
        return add(bigram(aWord1, aWord2));
    }

    // Bigram-frequency inverse-proximity-frequency
    public double bfipf(Bigram b) {
        double result = 0;
        result = ((double) get(b)) / frequency(b.getWords());
        return result;
    }

    public JsonNode toJson() {
        ObjectNode result = MAPPER.createObjectNode();
        ArrayNode bigramsArray = MAPPER.createArrayNode();

        SortedArrayList<Bigram> bigrams = new SortedArrayList<Bigram>();
        for (Bigram b : this) {
            bigrams.sortedAdd(b, bfipf(b));
        }

        for (Bigram b : bigrams) {
            ObjectNode bigramNode = b.toJson();
            bigramNode.put("frequency", get(b));
            bigramNode.put("bfipf", bfipf(b));
            bigramsArray.add(bigramNode);
        }
        result.set("bigrams", bigramsArray);

        return result;
    }

    // ------------------------------------------------------------------------------------------ //
    // Private
    // ------------------------------------------------------------------------------------------ //
    private Bigram bigram(String aWord1, String aWord2) {
        return new Bigram(aWord1, aWord2);
    }

    private final int frequency(List<String> aList) {
        return frequency(aList.get(0)) * frequency(aList.get(1));
    }

    private final int frequency(String aWord) {
        return _frequencies.get(aWord);
    }

    private final FrequencyHashtable<String> _frequencies = new FrequencyHashtable<String>();
    private static final ObjectMapper MAPPER = new ObjectMapper();

}