Java tutorial
/* * 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.math3.stat; import java.io.Serializable; import java.text.NumberFormat; import java.util.Collection; import java.util.Iterator; import java.util.Comparator; import java.util.Map; import java.util.TreeMap; import org.apache.commons.math3.exception.MathIllegalArgumentException; import org.apache.commons.math3.exception.util.LocalizedFormats; /** * Maintains a frequency distribution. * <p> * Accepts int, long, char or Comparable values. New values added must be * comparable to those that have been added, otherwise the add method will * throw an IllegalArgumentException.</p> * <p> * Integer values (int, long, Integer, Long) are not distinguished by type -- * i.e. <code>addValue(Long.valueOf(2)), addValue(2), addValue(2l)</code> all have * the same effect (similarly for arguments to <code>getCount,</code> etc.).</p> * <p> * char values are converted by <code>addValue</code> to Character instances. * As such, these values are not comparable to integral values, so attempts * to combine integral types with chars in a frequency distribution will fail. * </p> * <p> * The values are ordered using the default (natural order), unless a * <code>Comparator</code> is supplied in the constructor.</p> * * @version $Id: Frequency.java 1422313 2012-12-15 18:53:41Z psteitz $ */ public class Frequency implements Serializable { /** Serializable version identifier */ private static final long serialVersionUID = -3845586908418844111L; /** underlying collection */ private final TreeMap<Comparable<?>, Long> freqTable; /** * Default constructor. */ public Frequency() { freqTable = new TreeMap<Comparable<?>, Long>(); } /** * Constructor allowing values Comparator to be specified. * * @param comparator Comparator used to order values */ @SuppressWarnings("unchecked") // TODO is the cast OK? public Frequency(Comparator<?> comparator) { freqTable = new TreeMap<Comparable<?>, Long>((Comparator<? super Comparable<?>>) comparator); } /** * Return a string representation of this frequency * distribution. * * @return a string representation. */ @Override public String toString() { NumberFormat nf = NumberFormat.getPercentInstance(); StringBuilder outBuffer = new StringBuilder(); outBuffer.append("Value \t Freq. \t Pct. \t Cum Pct. \n"); Iterator<Comparable<?>> iter = freqTable.keySet().iterator(); while (iter.hasNext()) { Comparable<?> value = iter.next(); outBuffer.append(value); outBuffer.append('\t'); outBuffer.append(getCount(value)); outBuffer.append('\t'); outBuffer.append(nf.format(getPct(value))); outBuffer.append('\t'); outBuffer.append(nf.format(getCumPct(value))); outBuffer.append('\n'); } return outBuffer.toString(); } /** * Adds 1 to the frequency count for v. * <p> * If other objects have already been added to this Frequency, v must * be comparable to those that have already been added. * </p> * * @param v the value to add. * @throws MathIllegalArgumentException if <code>v</code> is not comparable with previous entries */ public void addValue(Comparable<?> v) throws MathIllegalArgumentException { incrementValue(v, 1); } /** * Increments the frequency count for v. * <p> * If other objects have already been added to this Frequency, v must * be comparable to those that have already been added. * </p> * * @param v the value to add. * @param increment the amount by which the value should be incremented * @throws IllegalArgumentException if <code>v</code> is not comparable with previous entries * @since 3.1 */ public void incrementValue(Comparable<?> v, long increment) { Comparable<?> obj = v; if (v instanceof Integer) { obj = Long.valueOf(((Integer) v).longValue()); } try { Long count = freqTable.get(obj); if (count == null) { freqTable.put(obj, Long.valueOf(increment)); } else { freqTable.put(obj, Long.valueOf(count.longValue() + increment)); } } catch (ClassCastException ex) { //TreeMap will throw ClassCastException if v is not comparable throw new MathIllegalArgumentException(LocalizedFormats.INSTANCES_NOT_COMPARABLE_TO_EXISTING_VALUES, v.getClass().getName()); } } /** * Adds 1 to the frequency count for v. * * @param v the value to add. * @throws MathIllegalArgumentException if the table contains entries not * comparable to Integer */ public void addValue(int v) throws MathIllegalArgumentException { addValue(Long.valueOf(v)); } /** * Adds 1 to the frequency count for v. * * @param v the value to add. * @throws MathIllegalArgumentException if the table contains entries not * comparable to Long */ public void addValue(long v) throws MathIllegalArgumentException { addValue(Long.valueOf(v)); } /** * Adds 1 to the frequency count for v. * * @param v the value to add. * @throws MathIllegalArgumentException if the table contains entries not * comparable to Char */ public void addValue(char v) throws MathIllegalArgumentException { addValue(Character.valueOf(v)); } /** Clears the frequency table */ public void clear() { freqTable.clear(); } /** * Returns an Iterator over the set of values that have been added. * <p> * If added values are integral (i.e., integers, longs, Integers, or Longs), * they are converted to Longs when they are added, so the objects returned * by the Iterator will in this case be Longs.</p> * * @return values Iterator */ public Iterator<Comparable<?>> valuesIterator() { return freqTable.keySet().iterator(); } /** * Return an Iterator over the set of keys and values that have been added. * Using the entry set to iterate is more efficient in the case where you * need to access respective counts as well as values, since it doesn't * require a "get" for every key...the value is provided in the Map.Entry. * <p> * If added values are integral (i.e., integers, longs, Integers, or Longs), * they are converted to Longs when they are added, so the values of the * map entries returned by the Iterator will in this case be Longs.</p> * * @return entry set Iterator * @since 3.1 */ public Iterator<Map.Entry<Comparable<?>, Long>> entrySetIterator() { return freqTable.entrySet().iterator(); } //------------------------------------------------------------------------- /** * Returns the sum of all frequencies. * * @return the total frequency count. */ public long getSumFreq() { long result = 0; Iterator<Long> iterator = freqTable.values().iterator(); while (iterator.hasNext()) { result += iterator.next().longValue(); } return result; } /** * Returns the number of values = v. * Returns 0 if the value is not comparable. * * @param v the value to lookup. * @return the frequency of v. */ public long getCount(Comparable<?> v) { if (v instanceof Integer) { return getCount(((Integer) v).longValue()); } long result = 0; try { Long count = freqTable.get(v); if (count != null) { result = count.longValue(); } } catch (ClassCastException ex) { // NOPMD // ignore and return 0 -- ClassCastException will be thrown if value is not comparable } return result; } /** * Returns the number of values = v. * * @param v the value to lookup. * @return the frequency of v. */ public long getCount(int v) { return getCount(Long.valueOf(v)); } /** * Returns the number of values = v. * * @param v the value to lookup. * @return the frequency of v. */ public long getCount(long v) { return getCount(Long.valueOf(v)); } /** * Returns the number of values = v. * * @param v the value to lookup. * @return the frequency of v. */ public long getCount(char v) { return getCount(Character.valueOf(v)); } /** * Returns the number of values in the frequency table. * * @return the number of unique values that have been added to the frequency table. * @see #valuesIterator() */ public int getUniqueCount() { return freqTable.keySet().size(); } /** * Returns the percentage of values that are equal to v * (as a proportion between 0 and 1). * <p> * Returns <code>Double.NaN</code> if no values have been added.</p> * * @param v the value to lookup * @return the proportion of values equal to v */ public double getPct(Comparable<?> v) { final long sumFreq = getSumFreq(); if (sumFreq == 0) { return Double.NaN; } return (double) getCount(v) / (double) sumFreq; } /** * Returns the percentage of values that are equal to v * (as a proportion between 0 and 1). * * @param v the value to lookup * @return the proportion of values equal to v */ public double getPct(int v) { return getPct(Long.valueOf(v)); } /** * Returns the percentage of values that are equal to v * (as a proportion between 0 and 1). * * @param v the value to lookup * @return the proportion of values equal to v */ public double getPct(long v) { return getPct(Long.valueOf(v)); } /** * Returns the percentage of values that are equal to v * (as a proportion between 0 and 1). * * @param v the value to lookup * @return the proportion of values equal to v */ public double getPct(char v) { return getPct(Character.valueOf(v)); } //----------------------------------------------------------------------------------------- /** * Returns the cumulative frequency of values less than or equal to v. * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup. * @return the proportion of values equal to v */ @SuppressWarnings({ "rawtypes", "unchecked" }) public long getCumFreq(Comparable<?> v) { if (getSumFreq() == 0) { return 0; } if (v instanceof Integer) { return getCumFreq(((Integer) v).longValue()); } Comparator<Comparable<?>> c = (Comparator<Comparable<?>>) freqTable.comparator(); if (c == null) { c = new NaturalComparator(); } long result = 0; try { Long value = freqTable.get(v); if (value != null) { result = value.longValue(); } } catch (ClassCastException ex) { return result; // v is not comparable } if (c.compare(v, freqTable.firstKey()) < 0) { return 0; // v is comparable, but less than first value } if (c.compare(v, freqTable.lastKey()) >= 0) { return getSumFreq(); // v is comparable, but greater than the last value } Iterator<Comparable<?>> values = valuesIterator(); while (values.hasNext()) { Comparable<?> nextValue = values.next(); if (c.compare(v, nextValue) > 0) { result += getCount(nextValue); } else { return result; } } return result; } /** * Returns the cumulative frequency of values less than or equal to v. * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup * @return the proportion of values equal to v */ public long getCumFreq(int v) { return getCumFreq(Long.valueOf(v)); } /** * Returns the cumulative frequency of values less than or equal to v. * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup * @return the proportion of values equal to v */ public long getCumFreq(long v) { return getCumFreq(Long.valueOf(v)); } /** * Returns the cumulative frequency of values less than or equal to v. * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup * @return the proportion of values equal to v */ public long getCumFreq(char v) { return getCumFreq(Character.valueOf(v)); } //---------------------------------------------------------------------------------------------- /** * Returns the cumulative percentage of values less than or equal to v * (as a proportion between 0 and 1). * <p> * Returns <code>Double.NaN</code> if no values have been added. * Returns 0 if at least one value has been added, but v is not comparable * to the values set.</p> * * @param v the value to lookup * @return the proportion of values less than or equal to v */ public double getCumPct(Comparable<?> v) { final long sumFreq = getSumFreq(); if (sumFreq == 0) { return Double.NaN; } return (double) getCumFreq(v) / (double) sumFreq; } /** * Returns the cumulative percentage of values less than or equal to v * (as a proportion between 0 and 1). * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup * @return the proportion of values less than or equal to v */ public double getCumPct(int v) { return getCumPct(Long.valueOf(v)); } /** * Returns the cumulative percentage of values less than or equal to v * (as a proportion between 0 and 1). * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup * @return the proportion of values less than or equal to v */ public double getCumPct(long v) { return getCumPct(Long.valueOf(v)); } /** * Returns the cumulative percentage of values less than or equal to v * (as a proportion between 0 and 1). * <p> * Returns 0 if v is not comparable to the values set.</p> * * @param v the value to lookup * @return the proportion of values less than or equal to v */ public double getCumPct(char v) { return getCumPct(Character.valueOf(v)); } //---------------------------------------------------------------------------------------------- /** * Merge another Frequency object's counts into this instance. * This Frequency's counts will be incremented (or set when not already set) * by the counts represented by other. * * @param other the other {@link Frequency} object to be merged * @since 3.1 */ public void merge(Frequency other) { for (Iterator<Map.Entry<Comparable<?>, Long>> iter = other.entrySetIterator(); iter.hasNext();) { Map.Entry<Comparable<?>, Long> entry = iter.next(); incrementValue(entry.getKey(), entry.getValue()); } } /** * Merge a {@link Collection} of {@link Frequency} objects into this instance. * This Frequency's counts will be incremented (or set when not already set) * by the counts represented by each of the others. * * @param others the other {@link Frequency} objects to be merged * @since 3.1 */ public void merge(Collection<Frequency> others) { for (Iterator<Frequency> iter = others.iterator(); iter.hasNext();) { merge(iter.next()); } } //---------------------------------------------------------------------------------------------- /** * A Comparator that compares comparable objects using the * natural order. Copied from Commons Collections ComparableComparator. */ private static class NaturalComparator<T extends Comparable<T>> implements Comparator<Comparable<T>>, Serializable { /** Serializable version identifier */ private static final long serialVersionUID = -3852193713161395148L; /** * Compare the two {@link Comparable Comparable} arguments. * This method is equivalent to: * <pre>(({@link Comparable Comparable})o1).{@link Comparable#compareTo compareTo}(o2)</pre> * * @param o1 the first object * @param o2 the second object * @return result of comparison * @throws NullPointerException when <i>o1</i> is <code>null</code>, * or when <code>((Comparable)o1).compareTo(o2)</code> does * @throws ClassCastException when <i>o1</i> is not a {@link Comparable Comparable}, * or when <code>((Comparable)o1).compareTo(o2)</code> does */ @SuppressWarnings("unchecked") // cast to (T) may throw ClassCastException, see Javadoc public int compare(Comparable<T> o1, Comparable<T> o2) { return o1.compareTo((T) o2); } } /** {@inheritDoc} */ @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((freqTable == null) ? 0 : freqTable.hashCode()); return result; } /** {@inheritDoc} */ @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (!(obj instanceof Frequency)) { return false; } Frequency other = (Frequency) obj; if (freqTable == null) { if (other.freqTable != null) { return false; } } else if (!freqTable.equals(other.freqTable)) { return false; } return true; } }