jsat.driftdetectors

Class BaseDriftDetector<V>

java.lang.Object

jsat.driftdetectors.BaseDriftDetector<V>

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

Direct Known Subclasses:

ADWIN, DDM

public abstract class BaseDriftDetector<V>
extends java.lang.Object
implements java.lang.Cloneable, java.io.Serializable

Base class for providing common functionality to drift detection algorithms

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
abstract boolean	addSample(double value, V obj) Adds a new point to the drift detector.
void	clearHistory() Clears the current history
abstract java.lang.Object	clone()
void	driftHandled() This method should be called once the drift is handled.
int	getDriftAge() Returns the number of items in recent history that differed from the historical values, or -1 if there has not been any detected drift.
java.util.List<V>	getDriftedHistory() Returns a new list containing up to getMaxHistory() objects in the history that drifted away from the prior state of the model.
int	getMaxHistory() Returns the maximum number of items that will be kept in the history.
boolean	isDrifting() Returns true if the algorithm believes that drift has definitely occurred.
boolean	isWarning() Returns true if the algorithm is in a warning state.
void	setMaxHistory(int maxHistory) Sets the maximum number of items to store in history.

Methods inherited from class java.lang.Object

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

Method Detail

isWarning

public boolean isWarning()

Returns true if the algorithm is in a warning state. This state indicates that the algorithm believes concept drift may be occurring, but is not confident enough to say that is had definitely occurred.
Not all algorithms will raise a warning state, and some may only begin keeping track of history once in the warning state.

Returns:

true if concept drift may have started, but is not sure

isDrifting

public boolean isDrifting()

Returns true if the algorithm believes that drift has definitely occurred. At this

Returns:

getMaxHistory

public int getMaxHistory()

Returns the maximum number of items that will be kept in the history.

Returns:

the maximum number of items that will be kept in the history.

setMaxHistory

public void setMaxHistory(int maxHistory)

Sets the maximum number of items to store in history. Setting this to 0 will keep the detector from ever storing history.
The user can still keep their own independent history or checkpoints by using the isDrifting() and isWarning() methods.

The history size may be changed at any time, but may result in the loss of history.

Parameters:

maxHistory - the new maximum history size of objects added

clearHistory

public void clearHistory()

Clears the current history

getDriftAge

public int getDriftAge()

Returns the number of items in recent history that differed from the historical values, or -1 if there has not been any detected drift. This method will return -1 even if isWarning() is true.

Returns:

the number of updates ago that the drift started, or -1 if no drift has occurred

getDriftedHistory

public java.util.List<V> getDriftedHistory()

Returns a new list containing up to getMaxHistory() objects in the history that drifted away from the prior state of the model.
The 0 index in the list will be the most recently added item, and the largest index will be the oldest item.

Returns:

the list of objects that make up the effected history

addSample

public abstract boolean addSample(double value,
                                  V obj)

Adds a new point to the drift detector. If an escalation in state occurs, true will be returned. A change of state could be either drift occurring isDrifting() or a warning state isWarning(). If the detector was in a warning state and then goes back to normal, false will be returned.

For binary (true / false) drift detectors, value will be considered false if and only if its value is equal to zero. Any non zero value will be treated as true

Objects added with the value may or may not be added to the history, the behavior is algorithm dependent. Some may always add it to the history, while others will only begin collecting history once a warning state occurs.

Parameters:

value - the numeric value to add to the drift detector

obj - the object associated with this value. It may or may not be stored in the detectors history

Returns:

true if a drift has or may be starting.

Throws:

UnhandledDriftException - if driftHandled() is not called after drifting is detected

driftHandled

public void driftHandled()

This method should be called once the drift is handled. Once done, this method will clear the flags and prepare the detector to continue tracking drift again.
By using this method, one can continue to track multiple future drift changes without having to feed the history data (which may be incomplete) into a new detector object.

clone

public abstract java.lang.Object clone()

Overrides:

clone in class java.lang.Object