Package org.apache.commons.statistics.descriptive

Class 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:
    Geometric mean (Wikipedia), SumOfLogs

    • Method Detail

      • 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.

      • 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.

      • 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.

      • 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.