edu.byu.nlp.util.Multisets2.java Source code

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Here is the source code for edu.byu.nlp.util.Multisets2.java

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/**
 * Copyright 2014 Brigham Young University
 *
 * 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 edu.byu.nlp.util;

import java.util.List;

import org.apache.commons.math3.random.RandomGenerator;

import com.google.common.collect.Multiset;

import edu.byu.nlp.util.ArgMinMaxTracker.MinMaxTracker;

/**
 * @author pfelt
 *
 */
public class Multisets2 {

    /**
     * Return the element(s) with the largest count in a multiset, or else null
     * if there are no elements (highest to lowest)
     */
    public static <T> List<T> maxElements(Multiset<T> mset, int topk, RandomGenerator rnd) {
        return getArgMinMax(rnd, topk, mset).argmax();
    }

    /**
     * Choose max element (arbitrary breaking ties)
     */
    public static <T> T maxElement(Multiset<T> mset, RandomGenerator rnd) {
        return getArgMinMax(rnd, 1, mset).argmin().get(0);
    }

    /**
     * @return the count of the element that appeared 
     * the largest number of times
     */
    public static <T> int maxCount(Multiset<T> mset) {
        return getMinMax(mset).max().get(0);
    }

    /**
     * Choose min k elements (arbitrary breaking ties). Ordered low to high.
     */
    public static <T> T minElements(Multiset<T> mset, int topk, RandomGenerator rnd) {
        return getArgMinMax(rnd, topk, mset).argmin().get(0);
    }

    /**
     * Choose an arbitrary min element
     */
    public static <T> T minElement(Multiset<T> mset, RandomGenerator rnd) {
        return getArgMinMax(rnd, 1, mset).argmin().get(0);
    }

    /**
     * @return the count of the element that appeared 
     * the fewest number of times
     */
    public static <T> int minCount(Multiset<T> mset) {
        return getMinMax(mset).min().get(0);
    }

    public static <T> MinMaxTracker<Integer> getMinMax(Multiset<T> mset) {
        MinMaxTracker<Integer> tracker = MinMaxTracker.create();
        for (com.google.common.collect.Multiset.Entry<T> entry : mset.entrySet()) {
            tracker.offer(entry.getCount(), entry.getElement());
        }
        return tracker;
    }

    public static <T> ArgMinMaxTracker<Integer, T> getArgMinMax(RandomGenerator rnd, int topk, Multiset<T> mset) {
        ArgMinMaxTracker<Integer, T> tracker = ArgMinMaxTracker.create(rnd, topk);
        for (com.google.common.collect.Multiset.Entry<T> entry : mset.entrySet()) {
            tracker.offer(entry.getCount(), entry.getElement());
        }
        return tracker;
    }
}