Class Statistics


  • public class Statistics
    extends Object
    A number of static methods to compute statistical properties of an array of double values. Implements the computation of mean, variance and standard deviation for double values.
    Since:
    0.11.0
    Author:
    Marco Schmidt
    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private Statistics()  
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static double computeMean​(double[] values)
      Computes the mean value for the argument array.
      static double computeMean​(double[] values, int offset, int number)
      Computes the mean value for some elements of the argument array.
      static double computeStandardDeviation​(double[] values)
      Computes the standard deviation for the argument array of values.
      static double computeStandardDeviation​(double[] values, double mean)
      Computes the standard deviation for the argument array of values.
      static double computeStandardDeviation​(double[] values, int offset, int number)
      Computes the standard deviation for some of the argument array's values.
      static double computeStandardDeviation​(double[] values, int offset, int number, double mean)
      Computes the standard deviation for some of the argument array's values.
      static double computeVariance​(double[] values)
      Computes the variance for the argument array.
      static double computeVariance​(double[] values, double mean)
      Computes the variance for some of the argument array's values.
      static double computeVariance​(double[] values, int offset, int number)
      Computes the variance for some of the argument array's values.
      static double computeVariance​(double[] values, int offset, int number, double mean)
      Computes the variance for some of the argument array's values.
    • Constructor Detail

      • Statistics

        private Statistics()
    • Method Detail

      • computeMean

        public static double computeMean​(double[] values)
        Computes the mean value for the argument array. Adds all values and divides them by the number of array elements.
        Parameters:
        values - double array on which the mean is to be determined
        Returns:
        computed mean value
        Throws:
        IllegalArgumentException - if the array has not at least one element
      • computeMean

        public static double computeMean​(double[] values,
                                         int offset,
                                         int number)
        Computes the mean value for some elements of the argument array. Adds all values and divides them by the number of array elements.
        Parameters:
        values - array from which elements are read
        offset - index of the first element to be used
        number - number of elements to be used
        Returns:
        computed mean value
        Throws:
        IllegalArgumentException - if the array has not at least one element
      • computeStandardDeviation

        public static double computeStandardDeviation​(double[] values)
        Computes the standard deviation for the argument array of values.
        Parameters:
        values - array from which elements are read
        Returns:
        computed standard deviation
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeStandardDeviation

        public static double computeStandardDeviation​(double[] values,
                                                      double mean)
        Computes the standard deviation for the argument array of values. Reuses the mean value for that argument which must have been computed before.
        Parameters:
        values - array from which elements are read
        mean - the mean value for the array, possibly computed with a call to computeMean(double[]).
        Returns:
        computed standard deviation
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeStandardDeviation

        public static double computeStandardDeviation​(double[] values,
                                                      int offset,
                                                      int number)
        Computes the standard deviation for some of the argument array's values. If you already have computed a mean value using computeMean(double[], int, int), better call computeStandardDeviation(double[], int, int, double). Otherwise, this method has to compute mean again.
        Parameters:
        values - array from which elements are read
        offset - first element to be used
        number - number of elements used starting at values[offset]
        Returns:
        computed standard deviation
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeStandardDeviation

        public static double computeStandardDeviation​(double[] values,
                                                      int offset,
                                                      int number,
                                                      double mean)
        Computes the standard deviation for some of the argument array's values. Use this version of the method if you already have a mean value, otherwise this method must be computed again.
        Parameters:
        values - array from which elements are read
        offset - first element to be used
        number - number of elements used starting at values[offset]
        mean - value of the elements
        Returns:
        computed standard deviation
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeVariance

        public static double computeVariance​(double[] values)
        Computes the variance for the argument array.
        Parameters:
        values - array from which elements are read
        Returns:
        variance for the array elements
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeVariance

        public static double computeVariance​(double[] values,
                                             double mean)
        Computes the variance for some of the argument array's values.
        Parameters:
        values - array from which elements are read
        mean - the mean for the array elements
        Returns:
        variance for the array elements
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeVariance

        public static double computeVariance​(double[] values,
                                             int offset,
                                             int number)
        Computes the variance for some of the argument array's values. If you already have computed a mean value using computeMean(double[], int, int), better call computeVariance(double[], int, int, double). Otherwise, this method has to compute mean again.
        Parameters:
        values - array from which elements are read
        offset - first element to be used
        number - number of elements used starting at values[offset]
        Returns:
        computed variance
        Throws:
        IllegalArgumentException - if the array has not at least two elements
      • computeVariance

        public static double computeVariance​(double[] values,
                                             int offset,
                                             int number,
                                             double mean)
        Computes the variance for some of the argument array's values. Use this version of the method in case mean has already been computed.
        Parameters:
        values - array from which elements are read
        offset - first element to be used
        number - number of elements used starting at values[offset]
        mean - the mean for the array elements
        Returns:
        computed variance
        Throws:
        IllegalArgumentException - if the array has not at least two elements