Package weka.classifiers.evaluation

Class CostCurve

java.lang.Object

weka.classifiers.evaluation.CostCurve

All Implemented Interfaces:

RevisionHandler

public class CostCurve
extends Object
implements RevisionHandler

Generates points illustrating probablity cost tradeoffs that can be obtained by varying the threshold value between classes. For example, the typical threshold value of 0.5 means the predicted probability of "positive" must be higher than 0.5 for the instance to be predicted as "positive".

Version:

$Revision$

Author:

Mark Hall (mhall@cs.waikato.ac.nz)

Field Summary

Fields

Modifier and Type	Field	Description
static String	NORM_EXPECTED_COST_NAME	attribute name: Normalized Expected Cost
static String	PROB_COST_FUNC_NAME	attribute name: Probability Cost Function
static String	RELATION_NAME	The name of the relation used in cost curve datasets
static String	THRESHOLD_NAME	attribute name: Threshold

Constructor Summary

Constructors

Constructor	Description
CostCurve()

Method Summary

Modifier and Type	Method	Description
Instances	getCurve(ArrayList<Prediction> predictions)	Calculates the performance stats for the default class and return results as a set of Instances.
Instances	getCurve(ArrayList<Prediction> predictions, int classIndex)	Calculates the performance stats for the desired class and return results as a set of Instances.
String	getRevision()	Returns the revision string.

Methods inherited from class java.lang.Object

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

Field Detail

RELATION_NAME

public static final String RELATION_NAME

The name of the relation used in cost curve datasets

See Also:

Constant Field Values

PROB_COST_FUNC_NAME

public static final String PROB_COST_FUNC_NAME

attribute name: Probability Cost Function

See Also:

Constant Field Values

NORM_EXPECTED_COST_NAME

public static final String NORM_EXPECTED_COST_NAME

attribute name: Normalized Expected Cost

See Also:

Constant Field Values

THRESHOLD_NAME

public static final String THRESHOLD_NAME

attribute name: Threshold

See Also:

Constant Field Values

Constructor Detail

CostCurve

public CostCurve()

Method Detail

getCurve

public Instances getCurve(ArrayList<Prediction> predictions)

Calculates the performance stats for the default class and return results as a set of Instances. The structure of these Instances is as follows:

• Probability Cost Function
• Normalized Expected Cost
• Threshold contains the probability threshold that gives rise to the previous performance values.

Parameters:

predictions - the predictions to base the curve on

Returns:

datapoints as a set of instances, null if no predictions have been made.

See Also:

TwoClassStats

getCurve

public Instances getCurve(ArrayList<Prediction> predictions,
                          int classIndex)

Calculates the performance stats for the desired class and return results as a set of Instances.

Parameters:

predictions - the predictions to base the curve on

classIndex - index of the class of interest.

Returns:

datapoints as a set of instances.

getRevision

public String getRevision()

Returns the revision string.

Specified by:

getRevision in interface RevisionHandler

Returns:

the revision