org.jscience.mathematics.statistics
Class LogisticDistribution

java.lang.Object
  extended by org.jscience.mathematics.statistics.Distribution
      extended by org.jscience.mathematics.statistics.LogisticDistribution
All Implemented Interfaces:
java.io.Serializable

public class LogisticDistribution
extends Distribution
implements java.io.Serializable

This class models the logistic distribution.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class org.jscience.mathematics.statistics.Distribution
CONTINUOUS, DISCRETE, MIXED
 
Constructor Summary
LogisticDistribution()
          This default constructor creates a new logsitic distribution and sets up the default computational domain (−7, 7).
 
Method Summary
 double getCDF(double x)
          This method computes the cumulative distribution function, which is F(x) = ex / (1 + ex)
 double getDensity(double x)
          This method computes the probability density function,which is f(x) = ex / (1 + ex)2
 double getMaxDensity()
          This method computes the maximum value of the density function, which is 1/4, the value of the density at x = 0.
 double getMean()
          This method returns the mean of the distribution, which is 0.
 double getMGF(double t)
          This method computes the moment generating function, which is Γ(1 + t) / Γ(1 − t).
 double getQuantile(double p)
          This method comptues the quantile function.
 double getVariance()
          This method computes the variance of the distribution, which is π2 / 3.
 java.lang.String toString()
          This method returns a string that gives the name of the distribution and the values of the parameters.
 
Methods inherited from class org.jscience.mathematics.statistics.Distribution
getDomain, getFailureRate, getMedian, getMoment, getMoment, getPGF, getSD, getType, setDomain, setDomain, simulate
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

LogisticDistribution

public LogisticDistribution()
This default constructor creates a new logsitic distribution and sets up the default computational domain (−7, 7).

Method Detail

getDensity

public double getDensity(double x)
This method computes the probability density function,which is f(x) = ex / (1 + ex)2

Specified by:
getDensity in class Distribution
Parameters:
x - a real number
Returns:
the probability density at x

getMaxDensity

public double getMaxDensity()
This method computes the maximum value of the density function, which is 1/4, the value of the density at x = 0.

Overrides:
getMaxDensity in class Distribution
Returns:
the maximum value of the density function

getCDF

public double getCDF(double x)
This method computes the cumulative distribution function, which is F(x) = ex / (1 + ex)

Overrides:
getCDF in class Distribution
Parameters:
x - a real number
Returns:
the cumulative probability at x

getQuantile

public double getQuantile(double p)
This method comptues the quantile function.

Overrides:
getQuantile in class Distribution
Parameters:
p - a probability in (0, 1)
Returns:
the quantile of order p

getMean

public double getMean()
This method returns the mean of the distribution, which is 0.

Overrides:
getMean in class Distribution
Returns:
the mean

getVariance

public double getVariance()
This method computes the variance of the distribution, which is π2 / 3.

Overrides:
getVariance in class Distribution
Returns:
the variance method in Distribution.

getMGF

public double getMGF(double t)
This method computes the moment generating function, which is Γ(1 + t) / Γ(1 − t).

Overrides:
getMGF in class Distribution
Parameters:
t - a number < 1
Returns:
the moment generating function at t

toString

public java.lang.String toString()
This method returns a string that gives the name of the distribution and the values of the parameters.

Overrides:
toString in class Distribution
Returns:
a string giving the name of the distribution and the values of the parameters