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

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

All Implemented Interfaces:

DifferentiableUnivariateFunction, UnivariateDifferentiableFunction, UnivariateFunction

public class Sigmoid
extends Object
implements UnivariateDifferentiableFunction, 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: Sigmoid.java 1455194 2013-03-11 15:45:54Z luc $

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.

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

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.

value

public DerivativeStructure value(DerivativeStructure t)
                          throws DimensionMismatchException

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:

DimensionMismatchException - if t is inconsistent with the function's free parameters or order

Since:

3.1