NDCGEvaluation (ELKI: Environment for DeveLoping KDD-Applications Supported by Index-Structures)

java.lang.Object
- elki.evaluation.scores.NDCGEvaluation

All Implemented Interfaces:

ScoreEvaluation
```
@Reference(authors="K. J\u00e4rvelin, J. Kek\u00e4l\u00e4inen",
           title="Cumulated gain-based evaluation of IR techniques",
           booktitle="ACM Transactions on Information Systems (TOIS)",
           url="https://doi.org/10.1145/582415.582418",
           bibkey="DBLP:journals/tois/JarvelinK02")
public class NDCGEvaluation
extends java.lang.Object
implements ScoreEvaluation
```
Normalized Discounted Cumulative Gain.
This evaluation metric would be able to use relevance information, but the current implementation is for binary labels only (it is easy to add, but requires API additions or changes).
Reference:
K. Järvelin, J. Kekäläinen
Cumulated gain-based evaluation of IR techniques
ACM Transactions on Information Systems (TOIS)
TODO: support weighted ground truth.

Since:

0.7.5

Author:

Erich Schubert

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class NDCGEvaluation.Par
Parameterization class.
- Nested classes/interfaces inherited from interface elki.evaluation.scores.ScoreEvaluation
  ScoreEvaluation.Adapter

Field Summary

Fields
Modifier and Type Field Description

static NDCGEvaluation STATIC
Static instance

Constructor Summary

Constructors
Constructor Description

NDCGEvaluation()

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static double`	`computeNDCG(ScoreEvaluation.Adapter adapter)`	Compute the DCG given a set of positive IDs and a sorted list of entries, which may include ties.
`double`	`evaluate(ScoreEvaluation.Adapter adapter)`	Evaluate a given predicate and iterator.
`double`	`expected(int pos, int all)`	Expected score for a random result.

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 NDCGEvaluation STATIC
```
    Static instance
- Constructor Detail
  - NDCGEvaluation
```
public NDCGEvaluation()
```
- 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
  - 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
  - computeNDCG
```
public static double computeNDCG(ScoreEvaluation.Adapter adapter)
```
    Compute the DCG given a set of positive IDs and a sorted list of entries, which may include ties.
    
    Parameters:
    
    adapter - Adapter for different input data types
    
    Returns:
    
    area under curve