edu.stanford.nlp.util
Class Counter

java.lang.Object
  extended byedu.stanford.nlp.util.Counter
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
DeltaCounter

public class Counter
extends Object
implements Serializable

A specialized kind of hash table (or map) for storing numeric counts for objects. It works like a Map, but with different methods for easily getting/setting/incrementing counts for objects and computing various functions with the counts. The Counter constructor and addAll method can be used to copy another Counter's contents over. This class also provides access to Comparators that can be used to sort the keys or entries of this Counter by the counts, in either ascending or descending order.

Author:
Dan Klein (klein@cs.stanford.edu), Joseph Smarr (jsmarr@stanford.edu), Teg Grenager, Galen Andrew, Christopher Manning
See Also:
Serialized Form

Constructor Summary
Counter()
          Constructs a new (empty) Counter.
Counter(Counter c)
          Constructs a new Counter with the contents of the given Counter.
Counter(MapFactory mapFactory)
          Pass in a MapFactory and the map it vends will back your counter.
 
Method Summary
 void addAll(Counter counter)
          Adds the counts in the given Counter to the counts in this Counter.
 Object argmax()
          Finds and returns the key in this Counter with the largest count.
 Object argmax(Comparator tieBreaker)
          Finds and returns the key in this Counter with the largest count.
 Object argmin()
          Finds and returns the key in this Counter with the smallest count.
 Object argmin(Comparator tieBreaker)
          Finds and returns the key in this Counter with the smallest count.
 Counter average(Counter other)
          Deprecated. Use Counters.average(Counter, Counter) instead.
 double averageCount()
          Returns the mean of all the counts (totalCount/size).
 void clear()
          Removes all counts from this Counter.
 Object clone()
           
 Comparator comparator()
          Comparator that sorts objects by (increasing) count.
 Comparator comparator(boolean ascending)
          Returns a comparator suitable for sorting this Counter's keys or entries by their respective counts.
 Comparator comparator(boolean ascending, boolean useMagnitude)
          Returns a comparator suitable for sorting this Counter's keys or entries by their respective value or magnitude (unsigned value).
 boolean containsKey(Object key)
           
 void decrementCount(Object key)
          Subtracts 1.0 from the count for the given key.
 void decrementCount(Object key, double count)
          Subtracts the given count from the current count for the given key.
 void decrementCounts(Collection keys)
          Subtracts 1.0 from the counts of each of the given keys.
 void decrementCounts(Collection keys, double count)
          Subtracts the given count from the current counts for each of the given keys.
 double entropy()
          Deprecated. Use Counters.entropy(Counter) instead.
 boolean equals(Object o)
           
 double getCount(Object key)
          Returns the current count for the given key, which is 0 if it hasn't been seen before.
 double getNormalizedCount(Object key)
          Deprecated. Create a Distribution instead.
 int hashCode()
           
 void incrementCount(Object key)
          Adds 1.0 to the count for the given key.
 void incrementCount(Object key, double count)
          Adds the given count to the current count for the given key.
 void incrementCounts(Collection keys)
          Adds 1.0 to the counts for each of the given keys.
 void incrementCounts(Collection keys, double count)
          Adds the given count to the current counts for each of the given keys.
 double informationRadius(Counter other)
          Deprecated. Use Counters.informationRadius(Counter, Counter) instead.
 boolean isEmpty()
           
 Set keysAbove(double countThreshold)
          Returns the set of keys whose counts are at or above the given threshold.
 Set keysAt(double count)
          Returns the set of keys that have exactly the given count.
 Set keysBelow(double countThreshold)
          Returns the set of keys whose counts are at or below the given threshold.
 Set keySet()
           
 double klDivergence(Counter other)
          Deprecated. Use Counters.klDivergence(Counter, Counter) instead.
static void main(String[] args)
          For internal debugging purposes only.
 double max()
          Finds and returns the largest count in this Counter.
 double min()
          Finds and returns the smallest count in this Counter.
 void normalize()
          Deprecated. Create a Distribution instead.
 Object remove(Object key)
          Removes the given key from this Counter.
 void removeAll(Collection c)
          Removes all the given keys from this Counter.
 void removeZeroCounts()
          Removes all keys whose count is 0.
 void setCount(Object key, double count)
          Sets the current count for the given key.
 void setCounts(Collection keys, double count)
          Sets the current count for each of the given keys.
 int size()
           
 void subtractAll(Counter counter)
          Subtracts the counts in the given Counter from the counts in this Counter.
 String toString()
           
 double totalCount()
          Returns the current total count for all objects in this Counter.
 double totalCount(Filter filter)
          Returns the total count for all objects in this Counter that pass the given Filter.
 
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Counter

public Counter()
Constructs a new (empty) Counter.


Counter

public Counter(MapFactory mapFactory)
Pass in a MapFactory and the map it vends will back your counter.


Counter

public Counter(Counter c)
Constructs a new Counter with the contents of the given Counter.

Method Detail

totalCount

public double totalCount()
Returns the current total count for all objects in this Counter. All counts are summed each time, so cache it if you need it repeatedly.


totalCount

public double totalCount(Filter filter)
Returns the total count for all objects in this Counter that pass the given Filter. Passing in a filter that always returns true is equivalent to calling totalCount().


averageCount

public double averageCount()
Returns the mean of all the counts (totalCount/size).


getCount

public double getCount(Object key)
Returns the current count for the given key, which is 0 if it hasn't been seen before. This is a convenient version of get that casts and extracts the primitive value.


getNormalizedCount

public double getNormalizedCount(Object key)
Deprecated. Create a Distribution instead.


setCount

public void setCount(Object key,
                     double count)
Sets the current count for the given key. This will wipe out any existing count for that key.

To add to a count instead of replacing it, use incrementCount(Object,double).


setCounts

public void setCounts(Collection keys,
                      double count)
Sets the current count for each of the given keys. This will wipe out any existing counts for these keys.

To add to the counts of a collection of objects instead of replacing them, use incrementCounts(Collection,double).


incrementCount

public void incrementCount(Object key,
                           double count)
Adds the given count to the current count for the given key. If the key hasn't been seen before, it is assumed to have count 0, and thus this method will set its count to the given amount. Negative increments are equivalent to calling decrementCount.

To more conviently increment the count by 1.0, use incrementCount(Object).

To set a count to a specifc value instead of incrementing it, use setCount(Object,double).


incrementCount

public void incrementCount(Object key)
Adds 1.0 to the count for the given key. If the key hasn't been seen before, it is assumed to have count 0, and thus this method will set its count to 1.0.

To increment the count by a value other than 1.0, use incrementCount(Object,double).

To set a count to a specifc value instead of incrementing it, use setCount(Object,double).


incrementCounts

public void incrementCounts(Collection keys,
                            double count)
Adds the given count to the current counts for each of the given keys. If any of the keys haven't been seen before, they are assumed to have count 0, and thus this method will set their counts to the given amount. Negative increments are equivalent to calling decrementCounts.

To more conviniently increment the counts of a collection of objects by 1.0, use incrementCounts(Collection).

To set the counts of a collection of objects to a specific value instead of incrementing them, use setCounts(Collection,double).


incrementCounts

public void incrementCounts(Collection keys)
Adds 1.0 to the counts for each of the given keys. If any of the keys haven't been seen before, they are assumed to have count 0, and thus this method will set their counts to 1.0.

To increment the counts of a collection of object by a value other than 1.0, use incrementCounts(Collection,double).

To set the counts of a collection of objects to a specifc value instead of incrementing them, use setCounts(Collection,double).


decrementCount

public void decrementCount(Object key,
                           double count)
Subtracts the given count from the current count for the given key. If the key hasn't been seen before, it is assumed to have count 0, and thus this method will set its count to the negative of the given amount. Negative increments are equivalent to calling incrementCount.

To more conviently decrement the count by 1.0, use decrementCount(Object).

To set a count to a specifc value instead of decrementing it, use setCount(Object,double).


decrementCount

public void decrementCount(Object key)
Subtracts 1.0 from the count for the given key. If the key hasn't been seen before, it is assumed to have count 0, and thus this method will set its count to -1.0.

To decrement the count by a value other than 1.0, use decrementCount(Object,double).

To set a count to a specifc value instead of decrementing it, use setCount(Object,double).


decrementCounts

public void decrementCounts(Collection keys,
                            double count)
Subtracts the given count from the current counts for each of the given keys. If any of the keys haven't been seen before, they are assumed to have count 0, and thus this method will set their counts to the negative of the given amount. Negative increments are equivalent to calling incrementCounts.

To more conviniently decrement the counts of a collection of objects by 1.0, use decrementCounts(Collection).

To set the counts of a collection of objects to a specific value instead of decrementing them, use setCounts(Collection,double).


decrementCounts

public void decrementCounts(Collection keys)
Subtracts 1.0 from the counts of each of the given keys. If any of the keys haven't been seen before, they are assumed to have count 0, and thus this method will set their counts to -1.0.

To decrement the counts of a collection of object by a value other than 1.0, use decrementCounts(Collection,double).

To set the counts of a collection of objects to a specifc value instead of decrementing them, use setCounts(Collection,double).


addAll

public void addAll(Counter counter)
Adds the counts in the given Counter to the counts in this Counter.

To copy the values from another Counter rather than adding them, use


subtractAll

public void subtractAll(Counter counter)
Subtracts the counts in the given Counter from the counts in this Counter.

To copy the values from another Counter rather than subtracting them, use


containsKey

public boolean containsKey(Object key)

remove

public Object remove(Object key)
Removes the given key from this Counter. Its count will now be 0 and it will no longer be considered previously seen.


removeAll

public void removeAll(Collection c)
Removes all the given keys from this Counter.


clear

public void clear()
Removes all counts from this Counter.


size

public int size()

isEmpty

public boolean isEmpty()

keySet

public Set keySet()

equals

public boolean equals(Object o)

hashCode

public int hashCode()

toString

public String toString()

clone

public Object clone()

normalize

public void normalize()
Deprecated. Create a Distribution instead.


removeZeroCounts

public void removeZeroCounts()
Removes all keys whose count is 0. After incrementing and decrementing counts or adding and subtracting Counters, there may be keys left whose count is 0, though normally this is undesirable. This method cleans up the map.

Maybe in the future we should try to do this more on-the-fly, though it's not clear whether a distinction should be made between "never seen" (i.e. null count) and "seen with 0 count". Certainly there's no distinction in getCount() but there is in containsKey().


max

public double max()
Finds and returns the largest count in this Counter.


min

public double min()
Finds and returns the smallest count in this Counter.


argmax

public Object argmax(Comparator tieBreaker)
Finds and returns the key in this Counter with the largest count. Ties are broken by comparing the objects using the given tie breaking Comparator, favoring Objects that are sorted to the front. This is useful if the keys are numeric and there is a bias to prefer smaller or larger values, and can be useful in other circumstances where random tie-breaking is not desirable. Returns null if this Counter is empty.


argmax

public Object argmax()
Finds and returns the key in this Counter with the largest count. Ties are broken according to the natural ordering of the objects. This will prefer smaller numeric keys and lexicographically earlier String keys. To use a different tie-breaking Comparator, use argmax(Comparator). Returns null if this Counter is empty.


argmin

public Object argmin(Comparator tieBreaker)
Finds and returns the key in this Counter with the smallest count. Ties are broken by comparing the objects using the given tie breaking Comparator, favoring Objects that are sorted to the front. This is useful if the keys are numeric and there is a bias to prefer smaller or larger values, and can be useful in other circumstances where random tie-breaking is not desirable. Returns null if this Counter is empty.


argmin

public Object argmin()
Finds and returns the key in this Counter with the smallest count. Ties are broken according to the natural ordering of the objects. This will prefer smaller numeric keys and lexicographically earlier String keys. To use a different tie-breaking Comparator, use argmin(Comparator). Returns null if this Counter is empty.


keysAbove

public Set keysAbove(double countThreshold)
Returns the set of keys whose counts are at or above the given threshold. This set may have 0 elements but will not be null.


keysBelow

public Set keysBelow(double countThreshold)
Returns the set of keys whose counts are at or below the given threshold. This set may have 0 elements but will not be null.


keysAt

public Set keysAt(double count)
Returns the set of keys that have exactly the given count. This set may have 0 elements but will not be null.


entropy

public double entropy()
Deprecated. Use Counters.entropy(Counter) instead.


klDivergence

public double klDivergence(Counter other)
Deprecated. Use Counters.klDivergence(Counter, Counter) instead.


informationRadius

public double informationRadius(Counter other)
Deprecated. Use Counters.informationRadius(Counter, Counter) instead.


average

public Counter average(Counter other)
Deprecated. Use Counters.average(Counter, Counter) instead.


comparator

public Comparator comparator(boolean ascending)
Returns a comparator suitable for sorting this Counter's keys or entries by their respective counts. If ascending is true, lower counts will be returned first, otherwise higher counts will be returned first.

Sample usage:

 Counter c = new Counter();
 // add to the counter...
 List biggestKeys = new ArrayList(c.keySet());
 Collections.sort(biggestKeys, c.comparator(false));
 List smallestEntries = new ArrayList(c.entrySet());
 Collections.sort(smallestEntries, c.comparator(true))
 


comparator

public Comparator comparator(boolean ascending,
                             boolean useMagnitude)
Returns a comparator suitable for sorting this Counter's keys or entries by their respective value or magnitude (unsigned value). If ascending is true, smaller magnitudes will be returned first, otherwise higher magnitudes will be returned first.

Sample usage:

 Counter c = new Counter();
 // add to the counter...
 List biggestKeys = new ArrayList(c.keySet());
 Collections.sort(biggestKeys, c.comparator(false, true));
 List smallestEntries = new ArrayList(c.entrySet());
 Collections.sort(smallestEntries, c.comparator(true))
 


comparator

public Comparator comparator()
Comparator that sorts objects by (increasing) count. Shortcut for calling comparator(true).


main

public static void main(String[] args)
                 throws Exception
For internal debugging purposes only.

Throws:
Exception


Stanford NLP Group