org.geotools.math

## Class Statistics

• All Implemented Interfaces:
Serializable, 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++) {
}
System.out.println(stats);

Since:
2.0
Author:
Martin Desruisseaux (IRD)
Serialized Form
• ### Nested Class Summary

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

Constructors
Constructor and Description
Statistics()
Constructs an initially empty set of statistics.
• ### Method Summary

All Methods
Modifier and Type Method and Description
Updates statistics for the specified sample.
Updates statistics for the specified sample.
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.
String toString()
Returns a string representation of this statistics.
String toString(Locale locale, boolean tabulations)
Returns a localized string representation of this statistics.
• ### Constructor Detail

• #### Statistics

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

• #### reset

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

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.

Updates statistics for the specified sample. This add method is usually invoked inside a for loop.
Parameters:
sample - The sample value.

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.
maximum()
• #### maximum

public double maximum()
Returns the maximum sample value, or NaN if none.
minimum()
• #### 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.
minimum(), maximum()
• #### 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 84.2% 1.5 93.3% 2 97.7% 3 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.
Overrides:
clone in class Object
Returns:
A copy of this object.
Object.clone()
• #### 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.