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

java.lang.Object
  org.apache.commons.math3.analysis.function.Logit

All Implemented Interfaces:

DifferentiableUnivariateFunction, UnivariateDifferentiableFunction, UnivariateFunction

public class Logit
extends Object
implements UnivariateDifferentiableFunction, DifferentiableUnivariateFunction

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

Since:

3.0

Version:

$Id: Logit.java 1391927 2012-09-30 00:03:30Z erans $

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() Deprecated. as of 3.1, replaced by value(DerivativeStructure)
DerivativeStructure	value(DerivativeStructure t) Simple mathematical 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)
             throws OutOfRangeException

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.

Throws:

OutOfRangeException

derivative

@Deprecated
public UnivariateFunction derivative()

Deprecated. as of 3.1, replaced by value(DerivativeStructure)

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)
                     throws OutOfRangeException

Parameters:

x - Value at which to compute the logit.

lo - Lower bound.

hi - Higher bound.

Returns:

the value of the logit function at x.

Throws:

OutOfRangeException - if x < lo or x > hi.

value

public DerivativeStructure value(DerivativeStructure t)
                          throws OutOfRangeException

Simple mathematical function.

UnivariateDifferentiableFunction classes compute both the value and the first derivative of the function.

Specified by:

value in interface UnivariateDifferentiableFunction

Parameters:

t - function input value

Returns:

function result

Throws:

OutOfRangeException - if parameter is outside of function domain

Since:

3.1