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net.sourceforge.jiu.util
Class Statistics

java.lang.Object
  extended bynet.sourceforge.jiu.util.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

Method Summary
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.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

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

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Copyright © 2000, 2001, 2002, 2003, 2004 Marco Schmidt