ExponentialDecayFunction

java.lang.Object
- org.apache.commons.math3.ml.neuralnet.sofm.util.ExponentialDecayFunction

```
public class ExponentialDecayFunction
extends java.lang.Object
```
Exponential decay function: a e^{-x / b}, where x is the (integer) independent variable.
Class is immutable.

Since:

3.3

Field Summary

Fields
Modifier and Type Field Description

private double a
Factor a.

private double oneOverB
Factor 1 / b.

Constructor Summary

Constructors
Constructor	Description
`ExponentialDecayFunction(double initValue, double valueAtNumCall, long numCall)`	Creates an instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type Method Description

double value(long numCall)
Computes a e^{-numCall / b}.
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - a
```
private final double a
```
    Factor a.
  - oneOverB
```
private final double oneOverB
```
    Factor 1 / b.
- Constructor Detail
  - ExponentialDecayFunction
```
public ExponentialDecayFunction(double initValue,
                                double valueAtNumCall,
                                long numCall)
```
    Creates an instance. It will be such that
    
    a = initValue
    
    b = -numCall / ln(valueAtNumCall / initValue)
    Parameters:
    
    initValue - Initial value, i.e. value(0).
    
    valueAtNumCall - Value of the function at numCall.
    
    numCall - Argument for which the function returns valueAtNumCall.
    
    Throws:
    
    NotStrictlyPositiveException - if initValue <= 0.
    
    NotStrictlyPositiveException - if valueAtNumCall <= 0.
    
    NumberIsTooLargeException - if valueAtNumCall >= initValue.
    
    NotStrictlyPositiveException - if numCall <= 0.
- Method Detail
  - value
```
public double value(long numCall)
```
    Computes a e^{-numCall / b}.
    
    Parameters:
    
    numCall - Current step of the training task.
    
    Returns:
    
    the value of the function at numCall.