edu.uah.math.distributions
Class Distribution

java.lang.Object
  |
  +--edu.uah.math.distributions.Distribution

Direct Known Subclasses:

ContinuousUniformDistribution, Convolution, NormalDistribution, PoissonDistribution

public abstract class Distribution

extends java.lang.Object

Distribution: An abstract implmentation of a real probability distribution

Field Summary

static int	CONTINUOUS
static int	DISCRETE
static int	MIXED

Constructor Summary

Distribution()

Method Summary

static double	betaCDF(double x, double a, double b) The method computes the beta CDF.
static double	comb(double n, int k) This method computes the number of combinations of k objects chosen from a population of n objects
static double	factorial(int k) This method computes k!
static double	gamma(double x) This method computes the gamma function.
static double	gammaCDF(double x, double a) This method computes the CDF of the gamma distribution with shape parameter a and scale parameter 1
double	getCDF(double x) This method returns a default approximate cumulative distribution function.
abstract double	getDensity(double x) The getDensity method is abstract and must be overridden for any specific distribuiton
Domain	getDomain() This method returns the domain of the distribution.
double	getFailureRate(double x) This method computes the failure rate function
double	getMaxDensity() This method returns the largest (finite) value of the getDensity function on the finite set of domain values.
double	getMean() This method returns a default approximate mean, based on the finite set of domain values.
double	getMedian() This method computes a default approximate median.
double	getQuantile(double p) This method computes an approximate getQuantile function.
double	getSD() This method returns the standard deviation, as the square root of the variance
int	getType() This method returns the type of the distribution (discrete or continuous)
double	getVariance() This method returns a default approximate variance.
static double	logGamma(double x) This method computes the log of the gamma function.
static double	perm(double n, int k) This method computes the number of permuatations of k objects chosen from a population of n objects.
void	setParameters(double a, double b, double w, int t) This method defines a partition of an interval that acts as a default domain for the distribution, for purposes of data collection and for default computations.
double	simulate() This method computes a default simulation of a value from the distribution, as a random getQuantile.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DISCRETE

public static final int DISCRETE

See Also:

Constant Field Values

CONTINUOUS

public static final int CONTINUOUS

See Also:

Constant Field Values

MIXED

public static final int MIXED

See Also:

Constant Field Values

Constructor Detail

Distribution

public Distribution()

Method Detail

getDensity

public abstract double getDensity(double x)

The getDensity method is abstract and must be overridden for any specific distribuiton

setParameters

public void setParameters(double a,
                          double b,
                          double w,
                          int t)

This method defines a partition of an interval that acts as a default domain for the distribution, for purposes of data collection and for default computations. For a discrete distribution, the specified parameters define the midpoints of the partition (these are typically the values on which the distribution is defined, although truncated if the true set of values is infinite). For a continuous distribution, the parameters define the boundary points of the interval on which the distribuiton is defined (truncated if the true interval is infinite)

getDomain

public Domain getDomain()

This method returns the domain of the distribution.

getType

public final int getType()

This method returns the type of the distribution (discrete or continuous)

getMaxDensity

public double getMaxDensity()

This method returns the largest (finite) value of the getDensity function on the finite set of domain values. This method should be overridden if the maximum value is known in closed form

getMean

public double getMean()

This method returns a default approximate mean, based on the finite set of domain values. This method should be overriden if the mean is known in closed form

getVariance

public double getVariance()

This method returns a default approximate variance. This method should be overriden if the variance is known in closed form

getSD

public double getSD()

This method returns the standard deviation, as the square root of the variance

getCDF

public double getCDF(double x)

This method returns a default approximate cumulative distribution function. This should be overriden if the CDF is known in closed form

getQuantile

public double getQuantile(double p)

This method computes an approximate getQuantile function. This should be overriden if the getQuantile function is known in closed form

simulate

public double simulate()

This method computes a default simulation of a value from the distribution, as a random getQuantile. This method should be overridden if a better method of simulation is known.

getMedian

public double getMedian()

This method computes a default approximate median. This method should be overriden when there is a closed form expression for the median.

getFailureRate

public double getFailureRate(double x)

This method computes the failure rate function

perm

public static double perm(double n,
                          int k)

This method computes the number of permuatations of k objects chosen from a population of n objects.

factorial

public static double factorial(int k)

This method computes k!, the number of permutations of k objects.

comb

public static double comb(double n,
                          int k)

This method computes the number of combinations of k objects chosen from a population of n objects

logGamma

public static double logGamma(double x)

This method computes the log of the gamma function.

gamma

public static double gamma(double x)

This method computes the gamma function.

gammaCDF

public static double gammaCDF(double x,
                              double a)

This method computes the CDF of the gamma distribution with shape parameter a and scale parameter 1

betaCDF

public static double betaCDF(double x,
                             double a,
                             double b)

The method computes the beta CDF.