Class IntMean

java.lang.Object
org.apache.commons.statistics.descriptive.IntMean
All Implemented Interfaces:
DoubleSupplier, IntConsumer, IntSupplier, LongSupplier, IntStatistic, StatisticAccumulator<IntMean>, StatisticResult
public final class IntMean extends Object implements IntStatistic, StatisticAccumulator<IntMean>
Computes the arithmetic mean of the available values. Uses the following definition of the sample mean:

\[ \frac{1}{n} \sum_{i=1}^n x_i \]

where \( n \) is the number of samples.

  • The result is NaN if no values are added.

This class uses an exact integer sum to compute the mean. Supports up to 263 (exclusive) observations. This implementation does not check for overflow of the count.

This class is designed to work with (though does not require) streams.

This implementation is not thread safe. If multiple threads access an instance of this class concurrently, and at least one of the threads invokes the accept or combine method, it must be synchronized externally.

However, it is safe to use accept and combine as accumulator and combiner functions of Collector on a parallel stream, because the parallel implementation of Stream.collect() provides the necessary partitioning, isolation, and merging of results for safe and efficient parallel execution.

Since:
1.1
See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private long
    n
    Count of values that have been added.
    private static final long
    SMALL_N
    Limit for small sample size where the sum can exactly map to a double.
    private final Int128
    sum
    Sum of the values.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    private
    IntMean()
    Create an instance.
    private
    IntMean(Int128 sum, int n)
    Create an instance.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    accept(int value)
    Updates the state of the statistic to reflect the addition of value.
    IntMean
    combine(IntMean other)
    Combines the state of the other statistic into this one.
    (package private) static double
    computeMean(Int128 sum, long n)
    Compute the mean.
    static IntMean
    create()
    Creates an instance.
    (package private) static IntMean
    createFromRange(int[] values, int from, int to)
    Create an instance using the specified range of values.
    double
    getAsDouble()
    Gets the mean of all input values.
    static IntMean
    of(int... values)
    Returns an instance populated using the input values.
    static IntMean
    ofRange(int[] values, int from, int to)
    Returns an instance populated using the specified range of values.

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface IntConsumer

    andThen

    Methods inherited from interface StatisticResult

    getAsBigInteger, getAsInt, getAsLong

  • Field Details

    • SMALL_N

      private static final long SMALL_N
      Limit for small sample size where the sum can exactly map to a double. This is conservatively set using 2^21 values of 2^31 (2^21 ~ 2 million).
      See Also:

    • sum

      private final Int128 sum
      Sum of the values.

    • n

      private long n
      Count of values that have been added.

  • Constructor Details

    • IntMean

      private IntMean()
      Create an instance.

    • IntMean

      private IntMean(Int128 sum, int n)
      Create an instance.
      Parameters:
      sum - Sum of the values.
      n - Count of values that have been added.

  • Method Details

    • create

      public static IntMean create()
      Creates an instance.

      The initial result is NaN.

      Returns:
      IntMean instance.

    • of

      public static IntMean of(int... values)
      Returns an instance populated using the input values.
      Parameters:
      values - Values.
      Returns:
      IntMean instance.

    • ofRange

      public static IntMean ofRange(int[] values, int from, int to)
      Returns an instance populated using the specified range of values.
      Parameters:
      values - Values.
      from - Inclusive start of the range.
      to - Exclusive end of the range.
      Returns:
      IntMean instance.
      Throws:
      IndexOutOfBoundsException - if the sub-range is out of bounds
      Since:
      1.2

    • createFromRange

      static IntMean createFromRange(int[] values, int from, int to)
      Create an instance using the specified range of values.

      Warning: No range checks are performed.

      Parameters:
      values - Values.
      from - Inclusive start of the range.
      to - Exclusive end of the range.
      Returns:
      IntMean instance.

    • accept

      public void accept(int value)
      Updates the state of the statistic to reflect the addition of value.
      Specified by:
      accept in interface IntConsumer
      Parameters:
      value - Value.

    • getAsDouble

      public double getAsDouble()
      Gets the mean of all input values.

      When no values have been added, the result is NaN.

      Specified by:
      getAsDouble in interface DoubleSupplier
      Returns:
      mean of all values.

    • computeMean

      static double computeMean(Int128 sum, long n)
      Compute the mean.

      This is a helper method used in higher order moments.

      Parameters:
      sum - Sum of the values.
      n - Count of the values.
      Returns:
      the mean

    • combine

      public IntMean combine(IntMean other)
      Description copied from interface: StatisticAccumulator
      Combines the state of the other statistic into this one.
      Specified by:
      combine in interface StatisticAccumulator<IntMean>
      Parameters:
      other - Another statistic to be combined.
      Returns:
      this instance after combining other.