org.apache.commons.math3.analysis.function
Class Logit

java.lang.Object
  extended by org.apache.commons.math3.analysis.function.Logit
All Implemented Interfaces:
DifferentiableUnivariateFunction, UnivariateFunction

public class Logit
extends Object
implements DifferentiableUnivariateFunction

Logit function. It is the inverse of the sigmoid function.

Since:
3.0
Version:
$Id$

Nested Class Summary
static class Logit.Parametric
          Parametric function where the input array contains the parameters of the logit function, ordered as follows: Lower bound Higher bound
 
Field Summary
private  double hi
          Higher bound.
private  double lo
          Lower bound.
 
Constructor Summary
Logit()
          Usual logit function, where the lower bound is 0 and the higher bound is 1.
Logit(double lo, double hi)
          Logit function.
 
Method Summary
 UnivariateFunction derivative()
          Returns the derivative of the function
 double value(double x)
          Compute the value of the function.
private static double value(double x, double lo, double hi)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

lo

private final double lo
Lower bound.


hi

private final double hi
Higher bound.

Constructor Detail

Logit

public Logit()
Usual logit function, where the lower bound is 0 and the higher bound is 1.


Logit

public Logit(double lo,
             double hi)
Logit function.

Parameters:
lo - Lower bound of the function domain.
hi - Higher bound of the function domain.
Method Detail

value

public double value(double x)
Compute the value of the function.

Specified by:
value in interface UnivariateFunction
Parameters:
x - Point at which the function value should be computed.
Returns:
the value of the function.

derivative

public UnivariateFunction derivative()
Returns the derivative of the function

Specified by:
derivative in interface DifferentiableUnivariateFunction
Returns:
the derivative function

value

private static double value(double x,
                            double lo,
                            double hi)
Parameters:
x - Value at which to compute the logit.
lo - Lower bound.
hi - Higher bound.
Returns:
the value of the logit function at x.


Copyright (c) 2003-2013 Apache Software Foundation