Package org.geotools.metadata.math

Class Statistics

Object
Statistics
All Implemented Interfaces:
Serializable, Cloneable, Cloneable
Direct Known Subclasses:
Statistics.Delta
public class Statistics extends Object implements Cloneable, Serializable
Holds some statistics about a series of sample values. Given a series of sample values s0, s1, s2, s3..., this class computes minimum, maximum, mean, root mean square and standard deviation. Statistics are computed on the fly; the sample values are never stored in memory.

An instance of Statistics is initially empty (i.e. all statistical values are set to NaN). The statistics are updated every time an add(double) method is invoked with a non-NaN value. A typical usage of this class is: 

 double[] data = new double[1000];
 // (Compute some data values here...)

 Statistics stats = new Statistics();
 for (int i=0; i<data.length; i++) {
     stats.add(data[i]);
 }
 System.out.println(stats);
Since:
2.0
Author:
Martin Desruisseaux (IRD)
See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    Statistics.Delta
    Holds some statistics about a series of sample values and the difference between them.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Statistics()
    Constructs an initially empty set of statistics.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    add(double sample)
    Updates statistics for the specified sample.
    void
    add(long sample)
    Updates statistics for the specified sample.
    void
    add(Statistics stats)
    Updates statistics with all samples from the specified stats.
    Statistics
    clone()
    Returns a clone of this statistics.
    int
    count()
    Returns the number of samples, excluding NaN values.
    int
    countNaN()
    Returns the number of NaN samples.
    boolean
    equals(Object obj)
    Tests this statistics with the specified object for equality.
    int
    hashCode()
    Returns a hash code value for this statistics.
    double
    maximum()
    Returns the maximum sample value, or NaN if none.
    double
    mean()
    Returns the mean value, or NaN if none.
    double
    minimum()
    Returns the minimum sample value, or NaN if none.
    double
    range()
    Returns the range of sample values.
    void
    reset()
    Resets the statistics to their initial NaN values.
    double
    rms()
    Returns the root mean square, or NaN if none.
    double
    standardDeviation(boolean allPopulation)
    Retourne l'écart type des échantillons par rapport à la moyenne.
    final String
    toString()
    Returns a string representation of this statistics.
    String
    toString(Locale locale, boolean tabulations)
    Returns a localized string representation of this statistics.

    Methods inherited from class Object

    finalize, getClass, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • Statistics

      public Statistics()
      Constructs an initially empty set of statistics. All statistical values are initialized to Double.NaN.

  • Method Details

    • reset

      public void reset()
      Resets the statistics to their initial NaN values. This method reset this object state as if it was just created.

    • add

      public void add(double sample)
      Updates statistics for the specified sample. This add method is usually invoked inside a for loop.
      Parameters:
      sample - The sample value. NaN values are ignored.
      See Also:

    • add

      public void add(long sample)
      Updates statistics for the specified sample. This add method is usually invoked inside a for loop.
      Parameters:
      sample - The sample value.
      See Also:

    • add

      public void add(Statistics stats)
      Updates statistics with all samples from the specified stats. Invoking this method is equivalent (except for rounding errors) to invoking add for all samples that were added to stats.
      Parameters:
      stats - The statistics to be added to this, or null if none.

    • countNaN

      public int countNaN()
      Returns the number of NaN samples. NaN samples are ignored in all other statitical computation. This method count them for information purpose only.

    • count

      public int count()
      Returns the number of samples, excluding NaN values.

    • minimum

      public double minimum()
      Returns the minimum sample value, or NaN if none.
      See Also:

    • maximum

      public double maximum()
      Returns the maximum sample value, or NaN if none.
      See Also:

    • range

      public double range()
      Returns the range of sample values. This is equivalent to maximum - minimum, except for rounding error. If no samples were added, then returns NaN.
      See Also:

    • mean

      public double mean()
      Returns the mean value, or NaN if none.

    • rms

      public double rms()
      Returns the root mean square, or NaN if none.

    • standardDeviation

      public double standardDeviation(boolean allPopulation)
      Retourne l'écart type des échantillons par rapport à la moyenne. Si les données fournies aux différentes méthodes add(...) se distribuent selon une loi normale, alors l'écart type est la distance de part et d'autre de la moyenne dans lequel se trouveraient environ 84% des données. Le tableau ci-dessous donne le pourcentage approximatif des données que l'on trouve de part et d'autre de la moyenne à des distances telles que 2 ou 3 fois l'écart-type.
       0.5  69.1% 
       1.0  84.2% 
       1.5  93.3% 
       2.0  97.7% 
       3.0  99.9% 
      Parameters:
      allPopulation - La valeur true indique que les données fournies aux différentes méthodes add(...) représentent l'ensemble de la polulation. La valeur false indique que ces données ne représentent qu'un échantillon de la population, ce qui est généralement le cas. Si le nombre de données est élevé, alors les valeurs true et false donneront sensiblement les mêmes résultats.

    • clone

      public Statistics clone()
      Returns a clone of this statistics.
      Specified by:
      clone in interface Cloneable
      Overrides:
      clone in class Object
      Returns:
      A copy of this object.
      See Also:

    • equals

      public boolean equals(Object obj)
      Tests this statistics with the specified object for equality.
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Returns a hash code value for this statistics.
      Overrides:
      hashCode in class Object

    • toString

      public final String toString()
      Returns a string representation of this statistics. This method invokes toString(Locale, boolean) using the default locale and spaces separator.
      Overrides:
      toString in class Object

    • toString

      public String toString(Locale locale, boolean tabulations)
      Returns a localized string representation of this statistics. This string will span multiple lines, one for each statistical value. For example: 
           Compte:      8726
     Minimum:    6.853
     Maximum:    8.259
     Moyenne:    7.421
     RMS:        7.846
     Écart-type: 6.489
      If tabulations is true, then labels (e.g. "Minimum") and values (e.g. "6.853") are separated by tabulations. Otherwise, they are separated by spaces.