org.encog.engine.network.activation
Class ActivationRamp

java.lang.Object
  org.encog.engine.network.activation.ActivationRamp

All Implemented Interfaces:

Serializable, Cloneable, ActivationFunction

public class ActivationRamp
extends Object
implements ActivationFunction

A ramp activation function. This function has a high and low threshold. If the high threshold is exceeded a fixed value is returned. Likewise, if the low value is exceeded another fixed value is returned.

See Also:

Serialized Form

Field Summary

static int	PARAM_RAMP_HIGH The ramp high parameter.
static int	PARAM_RAMP_HIGH_THRESHOLD The ramp high threshold parameter.
static int	PARAM_RAMP_LOW The ramp low parameter.
static int	PARAM_RAMP_LOW_THRESHOLD The ramp low threshold parameter.

Constructor Summary

ActivationRamp()
Default constructor.

ActivationRamp(double thresholdHigh, double thresholdLow, double high, double low)
Construct a ramp activation function.

Method Summary

void	activationFunction(double[] x, int start, int size) Implements the activation function.
ActivationFunction	clone() Clone the object.
double	derivativeFunction(double b, double a) Calculate the derivative.
double	getHigh()
double	getLow()
String[]	getParamNames()
double[]	getParams()
double	getThresholdHigh()
double	getThresholdLow()
boolean	hasDerivative()
void	setHigh(double d) Set the high value.
void	setLow(double d) Set the low value.
void	setParam(int index, double value) Set one of the params for this activation function.
void	setThresholdHigh(double d) Set the threshold high.
void	setThresholdLow(double d) Set the threshold low.

Methods inherited from class java.lang.Object

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

Field Detail

PARAM_RAMP_HIGH_THRESHOLD

public static final int PARAM_RAMP_HIGH_THRESHOLD

The ramp high threshold parameter.

See Also:

Constant Field Values

PARAM_RAMP_LOW_THRESHOLD

public static final int PARAM_RAMP_LOW_THRESHOLD

The ramp low threshold parameter.

See Also:

Constant Field Values

PARAM_RAMP_HIGH

public static final int PARAM_RAMP_HIGH

The ramp high parameter.

See Also:

Constant Field Values

PARAM_RAMP_LOW

public static final int PARAM_RAMP_LOW

The ramp low parameter.

See Also:

Constant Field Values

Constructor Detail

ActivationRamp

public ActivationRamp()

Default constructor.

ActivationRamp

public ActivationRamp(double thresholdHigh,
                      double thresholdLow,
                      double high,
                      double low)

Construct a ramp activation function.

Parameters:

thresholdHigh - The high threshold value.

thresholdLow - The low threshold value.

high - The high value, replaced if the high threshold is exceeded.

low - The low value, replaced if the low threshold is exceeded.

Method Detail

activationFunction

public final void activationFunction(double[] x,
                                     int start,
                                     int size)

Implements the activation function. The array is modified according to the activation function being used. See the class description for more specific information on this type of activation function.

Specified by:

activationFunction in interface ActivationFunction

Parameters:

x - The input array to the activation function.

start - The starting index.

size - The number of values to calculate.

clone

public final ActivationFunction clone()

Clone the object.

Specified by:

clone in interface ActivationFunction

Overrides:

clone in class Object

Returns:

The cloned object.

derivativeFunction

public final double derivativeFunction(double b,
                                       double a)

Calculate the derivative. For performance reasons two numbers are provided. First, the value "b" is simply the number that we would like to calculate the derivative of. Second, the value "a", which is the value returned by the activation function, when presented with "b". We use two values because some of the most common activation functions make use of the result of the activation function. It is bad for performance to calculate this value twice. Yet, not all derivatives are calculated this way. By providing both the value before the activation function is applied ("b"), and after the activation function is applied("a"), the class can be constructed to use whichever value will be the most efficient.

Specified by:

derivativeFunction in interface ActivationFunction

Parameters:

b - The number to calculate the derivative of, the number "before" the activation function was applied.

a - The number "after" an activation function has been applied.

Returns:

The derivative.

getHigh

public final double getHigh()

Returns:

the high

getLow

public final double getLow()

Returns:

the low

getParamNames

public final String[] getParamNames()

Specified by:

getParamNames in interface ActivationFunction

Returns:

The names of the parameters.

getParams

public final double[] getParams()

Specified by:

getParams in interface ActivationFunction

Returns:

The params for this activation function.

getThresholdHigh

public final double getThresholdHigh()

Returns:

the thresholdHigh

getThresholdLow

public final double getThresholdLow()

Returns:

the thresholdLow

hasDerivative

public final boolean hasDerivative()

Specified by:

hasDerivative in interface ActivationFunction

Returns:

True, as this function does have a derivative.

setHigh

public final void setHigh(double d)

Set the high value.

Parameters:

d - The high value.

setLow

public final void setLow(double d)

Set the low value.

Parameters:

d - The low value.

setParam

public final void setParam(int index,
                           double value)

Set one of the params for this activation function.

Specified by:

setParam in interface ActivationFunction

Parameters:

index - The index of the param to set.

value - The value to set.

setThresholdHigh

public final void setThresholdHigh(double d)

Set the threshold high.

Parameters:

d - The threshold high.

setThresholdLow

public final void setThresholdLow(double d)

Set the threshold low.

Parameters:

d - The threshold low.