Class GeometricMean

java.lang.Object
org.apache.commons.statistics.descriptive.GeometricMean
All Implemented Interfaces:
DoubleConsumer, DoubleSupplier, IntSupplier, LongSupplier, DoubleStatistic, StatisticAccumulator<GeometricMean>, StatisticResult
public final class GeometricMean extends Object implements DoubleStatistic, StatisticAccumulator<GeometricMean>
Computes the geometric mean of the available values. Uses the following definition of the geometric mean:

\[ \left(\prod_{i=1}^n x_i\right)^\frac{1}{n} \]

where \( n \) is the number of samples. This implementation uses the log scale:

\[ \exp{\left( {\frac{1}{n}\sum_{i=1}^n \ln x_i} \right)} \]

  • The result is NaN if no values are added.
  • The result is NaN if any of the values is NaN.
  • The result is NaN if any of the values is negative.
  • The result is +infinity if all values are in the range (0, +infinity] and at least one value is +infinity.
  • The result is 0 if all values are in the range [0, +infinity) and at least one value is zero.
  • The result is NaN if all values are in the range [0, +infinity] and at least one value is zero, and one value is +infinity.

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 instance 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 instance of Stream.collect() provides the necessary partitioning, isolation, and merging of results for safe and efficient parallel execution.

Since:
1.1
See Also:

  • Field Details

    • n

      private long n
      Count of values that have been added.

    • sumOfLogs

      private final SumOfLogs sumOfLogs
      Sum of logs used to compute the geometric mean.

  • Constructor Details

    • GeometricMean

      private GeometricMean()
      Create an instance.

    • GeometricMean

      private GeometricMean(SumOfLogs sumOfLogs, long n)
      Create an instance.
      Parameters:
      sumOfLogs - Sum of logs.
      n - Count of values.

  • Method Details

    • create

      public static GeometricMean create()
      Creates an instance.

      The initial result is NaN.

      Returns:
      GeometricMean instance.

    • of

      public static GeometricMean of(double... values)
      Returns an instance populated using the input values.

      When the input is an empty array, the result is NaN.

      Parameters:
      values - Values.
      Returns:
      GeometricMean instance.

    • ofRange

      public static GeometricMean ofRange(double[] values, int from, int to)
      Returns an instance populated using the specified range of values.

      When the range is empty, the result is NaN.

      Parameters:
      values - Values.
      from - Inclusive start of the range.
      to - Exclusive end of the range.
      Returns:
      GeometricMean instance.
      Throws:
      IndexOutOfBoundsException - if the sub-range is out of bounds
      Since:
      1.2

    • of

      public static GeometricMean of(int... values)
      Returns an instance populated using the input values.

      When the input is an empty array, the result is NaN.

      Parameters:
      values - Values.
      Returns:
      GeometricMean instance.

    • ofRange

      public static GeometricMean ofRange(int[] values, int from, int to)
      Returns an instance populated using the specified range of values.

      When the range is empty, the result is NaN.

      Parameters:
      values - Values.
      from - Inclusive start of the range.
      to - Exclusive end of the range.
      Returns:
      GeometricMean instance.
      Throws:
      IndexOutOfBoundsException - if the sub-range is out of bounds
      Since:
      1.2

    • of

      public static GeometricMean of(long... values)
      Returns an instance populated using the input values.

      When the input is an empty array, the result is NaN.

      Parameters:
      values - Values.
      Returns:
      GeometricMean instance.

    • ofRange

      public static GeometricMean ofRange(long[] values, int from, int to)
      Returns an instance populated using the specified range of values.

      When the range is empty, the result is NaN.

      Parameters:
      values - Values.
      from - Inclusive start of the range.
      to - Exclusive end of the range.
      Returns:
      GeometricMean instance.
      Throws:
      IndexOutOfBoundsException - if the sub-range is out of bounds
      Since:
      1.2

    • accept

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

    • getAsDouble

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

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

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

    • combine

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

    • computeGeometricMean

      static double computeGeometricMean(long n, SumOfLogs sumOfLogs)
      Compute the geometric mean.
      Parameters:
      n - Count of values.
      sumOfLogs - Sum of logs.
      Returns:
      the geometric mean