Package elki.evaluation.scores

Class ROCEvaluation

java.lang.Object

elki.evaluation.scores.ROCEvaluation

All Implemented Interfaces:

ScoreEvaluation

public class ROCEvaluation
extends java.lang.Object
implements ScoreEvaluation

Compute ROC (Receiver Operating Characteristics) curves.

A ROC curve compares the true positive rate (y-axis) and false positive rate (x-axis).

It was first used in radio signal detection, but has since found widespread use in information retrieval, in particular for evaluating binary classification problems.

ROC curves are particularly useful to evaluate a ranking of objects with respect to a binary classification problem: a random sampling will approximately achieve a ROC value of 0.5, while a perfect separation will achieve 1.0 (all positives first) or 0.0 (all negatives first). In most use cases, a score significantly below 0.5 indicates that the algorithm result has been used the wrong way, and should be used backwards.

Since:

0.7.0

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ROCEvaluation.Par	Parameterization class.
static class	ROCEvaluation.ROCurve	ROC Curve

Nested classes/interfaces inherited from interface elki.evaluation.scores.ScoreEvaluation

ScoreEvaluation.Adapter

Field Summary

Fields

Modifier and Type	Field	Description
static ROCEvaluation	STATIC	Static instance

Constructor Summary

Constructors

Constructor	Description
ROCEvaluation()

Method Summary

Modifier and Type	Method	Description
static double	computeAUROC(ScoreEvaluation.Adapter adapter)	Compute the area under the ROC curve given a set of positive IDs and a sorted list of (comparable, ID)s, where the comparable object is used to decided when two objects are interchangeable.
double	evaluate(ScoreEvaluation.Adapter adapter)	Evaluate a given predicate and iterator.
double	expected(int pos, int all)	Expected score for a random result.
static ROCEvaluation.ROCurve	materializeROC(ScoreEvaluation.Adapter adapter)	Compute a ROC curve given a set of positive IDs and a sorted list of (comparable, ID)s, where the comparable object is used to decided when two objects are interchangeable.

Methods inherited from class java.lang.Object

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

Methods inherited from interface elki.evaluation.scores.ScoreEvaluation

evaluate

Field Detail

STATIC

public static final ROCEvaluation STATIC

Static instance

Constructor Detail

ROCEvaluation

public ROCEvaluation()

Method Detail

evaluate

public double evaluate(ScoreEvaluation.Adapter adapter)

Description copied from interface: ScoreEvaluation

Evaluate a given predicate and iterator.

Specified by:

evaluate in interface ScoreEvaluation

Parameters:

adapter - Input data adapter

Returns:

Score

materializeROC

public static ROCEvaluation.ROCurve materializeROC(ScoreEvaluation.Adapter adapter)

Compute a ROC curve given a set of positive IDs and a sorted list of (comparable, ID)s, where the comparable object is used to decided when two objects are interchangeable.

Parameters:

adapter - Adapter for different input data types

Returns:

area under curve

computeAUROC

public static double computeAUROC(ScoreEvaluation.Adapter adapter)

Compute the area under the ROC curve given a set of positive IDs and a sorted list of (comparable, ID)s, where the comparable object is used to decided when two objects are interchangeable.

Parameters:

adapter - Adapter for different input data types

Returns:

area under curve

expected

public double expected(int pos,
                       int all)

Description copied from interface: ScoreEvaluation

Expected score for a random result.

Specified by:

expected in interface ScoreEvaluation

Parameters:

pos - Number of positive elements

all - Total number of elements

Returns:

Expected score