## 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 Sigmoidextends Objectimplements 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 1391927 2012-09-30 00:03:30Z erans \$

Nested Class Summary
`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
`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
` 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.

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

```@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)`
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
Since:
3.1