org.apache.commons.math3.stat

## Class Frequency

- java.lang.Object
- - org.apache.commons.math3.stat.Frequency

- All Implemented Interfaces:
    Serializable

      public class Frequency
      extends Object
      implements Serializable

  Maintains a frequency distribution.

  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.

  Integer values (int, long, Integer, Long) are not distinguished by type -- i.e. `addValue(Long.valueOf(2)), addValue(2), addValue(2l)` all have the same effect (similarly for arguments to `getCount,` etc.).

  NOTE: byte and short values will be implicitly converted to int values by the compiler, thus there are no explicit overloaded methods for these primitive types.

  char values are converted by `addValue` 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.

  Float is not coerced to Double. Since they are not Comparable with each other the user must do any necessary coercion. Float.NaN and Double.NaN are not treated specially; they may occur in input and will occur in output if appropriate.

  The values are ordered using the default (natural order), unless a `Comparator` is supplied in the constructor.

  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Frequency()` Default constructor.
    `Frequency(Comparator<?> comparator)` Constructor allowing values Comparator to be specified.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addValue(char v)` Adds 1 to the frequency count for v.
    `void` | `addValue(Comparable<?> v)` Adds 1 to the frequency count for v.
    `void` | `addValue(int v)` Adds 1 to the frequency count for v.
    `void` | `addValue(long v)` Adds 1 to the frequency count for v.
    `void` | `clear()` Clears the frequency table
    `Iterator<Map.Entry<Comparable<?>,Long>>` | `entrySetIterator()` Return an Iterator over the set of keys and values that have been added.
    `boolean` | `equals(Object obj)`
    `long` | `getCount(char v)` Returns the number of values equal to v.
    `long` | `getCount(Comparable<?> v)` Returns the number of values equal to v.
    `long` | `getCount(int v)` Returns the number of values equal to v.
    `long` | `getCount(long v)` Returns the number of values equal to v.
    `long` | `getCumFreq(char v)` Returns the cumulative frequency of values less than or equal to v.
    `long` | `getCumFreq(Comparable<?> v)` Returns the cumulative frequency of values less than or equal to v.
    `long` | `getCumFreq(int v)` Returns the cumulative frequency of values less than or equal to v.
    `long` | `getCumFreq(long v)` Returns the cumulative frequency of values less than or equal to v.
    `double` | `getCumPct(char v)` Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).
    `double` | `getCumPct(Comparable<?> v)` Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).
    `double` | `getCumPct(int v)` Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).
    `double` | `getCumPct(long v)` Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).
    `List<Comparable<?>>` | `getMode()` Returns the mode value(s) in comparator order.
    `double` | `getPct(char v)` Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
    `double` | `getPct(Comparable<?> v)` Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
    `double` | `getPct(int v)` Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
    `double` | `getPct(long v)` Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
    `long` | `getSumFreq()` Returns the sum of all frequencies.
    `int` | `getUniqueCount()` Returns the number of values in the frequency table.
    `int` | `hashCode()`
    `void` | `incrementValue(char v, long increment)` Increments the frequency count for v.
    `void` | `incrementValue(Comparable<?> v, long increment)` Increments the frequency count for v.
    `void` | `incrementValue(int v, long increment)` Increments the frequency count for v.
    `void` | `incrementValue(long v, long increment)` Increments the frequency count for v.
    `void` | `merge(Collection<Frequency> others)` Merge a `Collection` of `Frequency` objects into this instance.
    `void` | `merge(Frequency other)` Merge another Frequency object's counts into this instance.
    `String` | `toString()` Return a string representation of this frequency distribution.
    `Iterator<Comparable<?>>` | `valuesIterator()` Returns an Iterator over the set of values that have been added.

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### Frequency

          public Frequency()

      Default constructor.

    - #### Frequency

          public Frequency(Comparator<?> comparator)

      Constructor allowing values Comparator to be specified.
      Parameters:
        `comparator` - Comparator used to order values

  - ### Method Detail

    - #### toString

          public String toString()

      Return a string representation of this frequency distribution.
      Overrides:
        `toString` in class `Object`
      Returns:
        a string representation.

    - #### addValue

          public void addValue(Comparable<?> v)
                        throws MathIllegalArgumentException

      Adds 1 to the frequency count for v.

      If other objects have already been added to this Frequency, v must be comparable to those that have already been added.

      Parameters:
        `v` - the value to add.
      Throws:
        `MathIllegalArgumentException` - if `v` is not comparable with previous entries

    - #### addValue

          public void addValue(int v)
                        throws MathIllegalArgumentException

      Adds 1 to the frequency count for v.
      Parameters:
        `v` - the value to add.
      Throws:
        `MathIllegalArgumentException` - if the table contains entries not comparable to Long

    - #### addValue

          public void addValue(long v)
                        throws MathIllegalArgumentException

      Adds 1 to the frequency count for v.
      Parameters:
        `v` - the value to add.
      Throws:
        `MathIllegalArgumentException` - if the table contains entries not comparable to Long

    - #### addValue

          public void addValue(char v)
                        throws MathIllegalArgumentException

      Adds 1 to the frequency count for v.
      Parameters:
        `v` - the value to add.
      Throws:
        `MathIllegalArgumentException` - if the table contains entries not comparable to Char

    - #### incrementValue

          public void incrementValue(Comparable<?> v,
                            long increment)
                              throws MathIllegalArgumentException

      Increments the frequency count for v.

      If other objects have already been added to this Frequency, v must be comparable to those that have already been added.

      Parameters:
        `v` - the value to add.
        `increment` - the amount by which the value should be incremented
      Throws:
        `MathIllegalArgumentException` - if `v` is not comparable with previous entries
      Since:
        3.1

    - #### incrementValue

          public void incrementValue(int v,
                            long increment)
                              throws MathIllegalArgumentException

      Increments the frequency count for v.

      If other objects have already been added to this Frequency, v must be comparable to those that have already been added.

      Parameters:
        `v` - the value to add.
        `increment` - the amount by which the value should be incremented
      Throws:
        `MathIllegalArgumentException` - if the table contains entries not comparable to Long
      Since:
        3.3

    - #### incrementValue

          public void incrementValue(long v,
                            long increment)
                              throws MathIllegalArgumentException

      Increments the frequency count for v.

      If other objects have already been added to this Frequency, v must be comparable to those that have already been added.

      Parameters:
        `v` - the value to add.
        `increment` - the amount by which the value should be incremented
      Throws:
        `MathIllegalArgumentException` - if the table contains entries not comparable to Long
      Since:
        3.3

    - #### incrementValue

          public void incrementValue(char v,
                            long increment)
                              throws MathIllegalArgumentException

      Increments the frequency count for v.

      If other objects have already been added to this Frequency, v must be comparable to those that have already been added.

      Parameters:
        `v` - the value to add.
        `increment` - the amount by which the value should be incremented
      Throws:
        `MathIllegalArgumentException` - if the table contains entries not comparable to Char
      Since:
        3.3

    - #### clear

          public void clear()

      Clears the frequency table

    - #### valuesIterator

          public Iterator<Comparable<?>> valuesIterator()

      Returns an Iterator over the set of values that have been added.

      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.

      Returns:
        values Iterator

    - #### entrySetIterator

          public Iterator<Map.Entry<Comparable<?>,Long>> entrySetIterator()

      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.

      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.

      Returns:
        entry set Iterator
      Since:
        3.1

    - #### getSumFreq

          public long getSumFreq()

      Returns the sum of all frequencies.
      Returns:
        the total frequency count.

    - #### getCount

          public long getCount(Comparable<?> v)

      Returns the number of values equal to v. Returns 0 if the value is not comparable.
      Parameters:
        `v` - the value to lookup.
      Returns:
        the frequency of v.

    - #### getCount

          public long getCount(int v)

      Returns the number of values equal to v.
      Parameters:
        `v` - the value to lookup.
      Returns:
        the frequency of v.

    - #### getCount

          public long getCount(long v)

      Returns the number of values equal to v.
      Parameters:
        `v` - the value to lookup.
      Returns:
        the frequency of v.

    - #### getCount

          public long getCount(char v)

      Returns the number of values equal to v.
      Parameters:
        `v` - the value to lookup.
      Returns:
        the frequency of v.

    - #### getUniqueCount

          public int getUniqueCount()

      Returns the number of values in the frequency table.
      Returns:
        the number of unique values that have been added to the frequency table.
      See Also:
        `valuesIterator()`

    - #### getPct

          public double getPct(Comparable<?> v)

      Returns the percentage of values that are equal to v (as a proportion between 0 and 1).

      Returns `Double.NaN` 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.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getPct

          public double getPct(int v)

      Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getPct

          public double getPct(long v)

      Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getPct

          public double getPct(char v)

      Returns the percentage of values that are equal to v (as a proportion between 0 and 1).
      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getCumFreq

          public long getCumFreq(Comparable<?> v)

      Returns the cumulative frequency of values less than or equal to v.

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup.
      Returns:
        the proportion of values equal to v

    - #### getCumFreq

          public long getCumFreq(int v)

      Returns the cumulative frequency of values less than or equal to v.

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getCumFreq

          public long getCumFreq(long v)

      Returns the cumulative frequency of values less than or equal to v.

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getCumFreq

          public long getCumFreq(char v)

      Returns the cumulative frequency of values less than or equal to v.

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values equal to v

    - #### getCumPct

          public double getCumPct(Comparable<?> v)

      Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).

      Returns `Double.NaN` 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.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values less than or equal to v

    - #### getCumPct

          public double getCumPct(int v)

      Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values less than or equal to v

    - #### getCumPct

          public double getCumPct(long v)

      Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values less than or equal to v

    - #### getCumPct

          public double getCumPct(char v)

      Returns the cumulative percentage of values less than or equal to v (as a proportion between 0 and 1).

      Returns 0 if v is not comparable to the values set.

      Parameters:
        `v` - the value to lookup
      Returns:
        the proportion of values less than or equal to v

    - #### getMode

          public List<Comparable<?>> getMode()

      Returns the mode value(s) in comparator order.
      Returns:
        a list containing the value(s) which appear most often.
      Since:
        3.3

    - #### merge

          public void merge(Frequency other)
                     throws NullArgumentException

      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.
      Parameters:
        `other` - the other `Frequency` object to be merged
      Throws:
        `NullArgumentException` - if `other` is null
      Since:
        3.1

    - #### merge

          public void merge(Collection<Frequency> others)
                     throws NullArgumentException

      Merge a `Collection` of `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.
      Parameters:
        `others` - the other `Frequency` objects to be merged
      Throws:
        `NullArgumentException` - if the collection is null
      Since:
        3.1

    - #### hashCode

          public int hashCode()

      Overrides:
        `hashCode` in class `Object`

    - #### equals

          public boolean equals(Object obj)

      Overrides:
        `equals` in class `Object`

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