Diversity (CF4J 2.3.0 API Documentation)

java.lang.Object
- es.upm.etsisi.cf4j.qualityMeasure.QualityMeasure
- - es.upm.etsisi.cf4j.qualityMeasure.recommendation.Diversity

```
public class Diversity
extends QualityMeasure
```
This class the averaged diversity of the recomendations. Diversity value is computed as explained in "Hurley, N., & Zhang, M. (2011). Novelty and diversity in top-n recommendation--analysis and evaluation. ACM Transactions on Internet Technology (TOIT), 10(4), 1-30.". Lower values denotes more diverse recommendations.

Field Summary
- Fields inherited from class es.upm.etsisi.cf4j.qualityMeasure.QualityMeasure
  recommender

Constructor Summary

Constructors
Constructor	Description
`Diversity(Recommender recommender, int numberOfRecommendations)`	Constructor of Diversity
`Diversity(Recommender recommender, Map<String,Object> params)`	Constructor from a Map object with the quality measure parameters.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected double`	`getScore(TestUser testUser, double[] predictions)`	Computes the quality measure score for a TestUser given the predictions for his/her test ratings

Methods inherited from class es.upm.etsisi.cf4j.qualityMeasure.QualityMeasure
getScore, getScore

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Diversity
```
public Diversity(Recommender recommender,
                 Map<String,Object> params)
```
    Constructor from a Map object with the quality measure parameters. Map object must contains the following keys:
    
    numberOfRecommendations: int value with the number of items to be recommended.
    Parameters:
    
    recommender - Recommender instance for which the Diversity are going to be computed
    
    params - Quality measure's parameters
  - Diversity
```
public Diversity(Recommender recommender,
                 int numberOfRecommendations)
```
    Constructor of Diversity
    
    Parameters:
    
    recommender - Recommender instance for which the precision are going to be computed
    
    numberOfRecommendations - Number of recommendations. It must be greater than 1
- Method Detail
  - getScore
```
protected double getScore(TestUser testUser,
                          double[] predictions)
```
    Description copied from class: QualityMeasure
    
    Computes the quality measure score for a TestUser given the predictions for his/her test ratings
    
    Specified by:
    
    getScore in class QualityMeasure
    
    Parameters:
    
    testUser - TestUser for which the quality measure score is computed
    
    predictions - Prediction value for the test items rated by the test user
    
    Returns:
    
    Quality measure score