org.apache.commons.math3.analysis.function

Class Sigmoid

java.lang.Object

org.apache.commons.math3.analysis.function.Sigmoid

All Implemented Interfaces:

DifferentiableUnivariateFunction, UnivariateFunction

public class Sigmoid
extends Object
implements DifferentiableUnivariateFunction

Sigmoid function. It is the inverse of the logit function. A more flexible version, the generalised logistic, is implemented by the Logistic class.

Since:

3.0

Version:

$Id$

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Sigmoid.Parametric Parametric function where the input array contains the parameters of the logit function, ordered as follows: Lower asymptote Higher asymptote

Constructor Summary

Constructors

Constructor and Description
Sigmoid() Usual sigmoid function, where the lower asymptote is 0 and the higher asymptote is 1.
Sigmoid(double lo, double hi) Sigmoid function.

Method Summary

Methods

Modifier and Type	Method and Description
UnivariateFunction	derivative() Returns the derivative of the function
double	value(double x) Compute the value of the function.

Methods inherited from class java.lang.Object

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

Constructor Detail

Sigmoid

public Sigmoid()

Usual sigmoid function, where the lower asymptote is 0 and the higher asymptote is 1.

Sigmoid

public Sigmoid(double lo,
       double hi)

Sigmoid function.

Parameters:

lo - Lower asymptote.

hi - Higher asymptote.

Method Detail

derivative

public UnivariateFunction derivative()

Returns the derivative of the function

Specified by:

derivative in interface DifferentiableUnivariateFunction

Returns:

the derivative function

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.