PSquarePercentile (Apache Commons Math 3.6.1 API)

org.apache.commons.math3.stat.descriptive.rank

## Class PSquarePercentile

- java.lang.Object
- - org.apache.commons.math3.stat.descriptive.AbstractUnivariateStatistic
  - - org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic
    - - org.apache.commons.math3.stat.descriptive.rank.PSquarePercentile

- All Implemented Interfaces:
    Serializable, StorelessUnivariateStatistic, UnivariateStatistic, MathArrays.Function

      public class PSquarePercentile
      extends AbstractStorelessUnivariateStatistic
      implements StorelessUnivariateStatistic, Serializable

  A `StorelessUnivariateStatistic` estimating percentiles using the P2 Algorithm as explained by Raj Jain and Imrich Chlamtac in P2 Algorithm for Dynamic Calculation of Quantiles and Histogram Without Storing Observations.

  Note: This implementation is not synchronized and produces an approximate result. For small samples, where data can be stored and processed in memory, `Percentile` should be used.

  See Also:
    Serialized Form

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected static interface` | `PSquarePercentile.PSquareMarkers` An interface that encapsulates abstractions of the P-square algorithm markers as is explained in the original works.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `PSquarePercentile(double p)` Constructs a PSquarePercentile with the specific percentile value.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `clear()` Clears the internal state of the Statistic
    `StorelessUnivariateStatistic` | `copy()` Returns a copy of the statistic with the same internal state.
    `boolean` | `equals(Object o)` Returns true iff `o` is a `PSquarePercentile` returning the same values as this for `getResult()` and `getN()` and also having equal markers
    `long` | `getN()` Returns the number of values that have been added.
    `double` | `getResult()` Returns the current value of the Statistic.
    `int` | `hashCode()` Returns hash code based on getResult() and getN()
    `void` | `increment(double observation)` Updates the internal state of the statistic to reflect the addition of the new value.
    `static PSquarePercentile.PSquareMarkers` | `newMarkers(List<Double> initialFive, double p)` A creation method to build Markers
    `double` | `quantile()` Returns the quantile estimated by this statistic in the range [0.0-1.0]
    `String` | `toString()` Returns a string containing the last observation, the current estimate of the quantile and all markers.

    - ### Methods inherited from class org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic

      `evaluate, evaluate, incrementAll, incrementAll`

    - ### Methods inherited from class org.apache.commons.math3.stat.descriptive.AbstractUnivariateStatistic

      `evaluate, getData, getDataRef, setData, setData, test, test, test, test`

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

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

    - ### Methods inherited from interface org.apache.commons.math3.stat.descriptive.StorelessUnivariateStatistic

      `incrementAll, incrementAll`

    - ### Methods inherited from interface org.apache.commons.math3.stat.descriptive.UnivariateStatistic

      `evaluate, evaluate`

- - ### Constructor Detail

    - #### PSquarePercentile

          public PSquarePercentile(double p)

      Constructs a PSquarePercentile with the specific percentile value.
      Parameters:
        `p` - the percentile
      Throws:
        `OutOfRangeException` - if p is not greater than 0 and less than or equal to 100

  - ### Method Detail

    - #### hashCode

          public int hashCode()

      Returns hash code based on getResult() and getN()
      Overrides:
        `hashCode` in class `AbstractStorelessUnivariateStatistic`
      Returns:
        hash code

    - #### equals

          public boolean equals(Object o)

      Returns true iff `o` is a `PSquarePercentile` returning the same values as this for `getResult()` and `getN()` and also having equal markers
      Overrides:
        `equals` in class `AbstractStorelessUnivariateStatistic`
      Parameters:
        `o` - object to compare
      Returns:
        true if `o` is a `PSquarePercentile` with equivalent internal state

    - #### increment

          public void increment(double observation)

      Updates the internal state of the statistic to reflect the addition of the new value.The internal state updated due to the new value in this context is basically of the marker positions and computation of the approximate quantile.
      Specified by:
        `increment` in interface `StorelessUnivariateStatistic`
      Specified by:
        `increment` in class `AbstractStorelessUnivariateStatistic`
      Parameters:
        `observation` - the observation currently being added.

    - #### toString

          public String toString()

      Returns a string containing the last observation, the current estimate of the quantile and all markers.
      Overrides:
        `toString` in class `Object`
      Returns:
        string representation of state data

    - #### getN

          public long getN()

      Returns the number of values that have been added.
      Specified by:
        `getN` in interface `StorelessUnivariateStatistic`
      Returns:
        the number of values.

    - #### copy

          public StorelessUnivariateStatistic copy()

      Returns a copy of the statistic with the same internal state.
      Specified by:
        `copy` in interface `StorelessUnivariateStatistic`
      Specified by:
        `copy` in interface `UnivariateStatistic`
      Specified by:
        `copy` in class `AbstractStorelessUnivariateStatistic`
      Returns:
        a copy of the statistic

    - #### quantile

          public double quantile()

      Returns the quantile estimated by this statistic in the range [0.0-1.0]
      Returns:
        quantile estimated by `getResult()`

    - #### clear

          public void clear()

      Clears the internal state of the Statistic. This basically clears all the markers, the initialFive list and sets countOfObservations to 0.
      Specified by:
        `clear` in interface `StorelessUnivariateStatistic`
      Specified by:
        `clear` in class `AbstractStorelessUnivariateStatistic`

    - #### getResult

          public double getResult()

      Returns the current value of the Statistic.
      Specified by:
        `getResult` in interface `StorelessUnivariateStatistic`
      Specified by:
        `getResult` in class `AbstractStorelessUnivariateStatistic`
      Returns:
        value of the statistic, `Double.NaN` if it has been cleared or just instantiated.

    - #### newMarkers

          public static PSquarePercentile.PSquareMarkers newMarkers(List<Double> initialFive,
                                                    double p)

      A creation method to build Markers
      Parameters:
        `initialFive` - list of initial five elements
        `p` - the quantile desired
      Returns:
        an instance of PSquareMarkers

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