ExponentialDecayFunction (Apache Commons Math 4.0-beta1)

java.lang.Object
- org.apache.commons.math4.neuralnet.sofm.util.ExponentialDecayFunction

All Implemented Interfaces:

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

Since:

3.3

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 applyAsDouble(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

- 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. applyAsDouble(0).
    
    valueAtNumCall - Value of the function at numCall.
    
    numCall - Argument for which the function returns valueAtNumCall.
    
    Throws:
    
    IllegalArgumentException - if initValue <= 0, valueAtNumCall <= 0, valueAtNumCall >= initValue or numCall <= 0.
- Method Detail
  - applyAsDouble
```
public double applyAsDouble(long numCall)
```
    Computes a e^{-numCall / b}.
    
    Specified by:
    
    applyAsDouble in interface LongToDoubleFunction
    
    Parameters:
    
    numCall - Current step of the training task.
    
    Returns:
    
    the value of the function at numCall.