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

java.lang.Object
- elki.itemsetmining.associationrules.interest.GiniIndex

All Implemented Interfaces:

InterestingnessMeasure
```
@Reference(authors="P. Tan, V. Kumar",title="Interestingness measures for association patterns: A perspective",booktitle="Proc. Workshop on Postprocessing in Machine Learning and Data Mining",url="https://www.cs.umn.edu/sites/cs.umn.edu/files/tech_reports/00-036.pdf",bibkey="tr/umn/TanK00") @Reference(authors="L. Breiman, J. H. Friedman, R. A. Olshen, C. J. Stone",title="Classification and Regression Trees",booktitle="",bibkey="books/wa/BreimanFOS84")
public class GiniIndex
extends java.lang.Object
implements InterestingnessMeasure
```
Gini-index based interestingness measure, using the weighted squared conditional probabilities compared to the non-conditional priors.
\[ P(X)\left(P(Y|X)^2+P(\neg Y|X)^2\right) + P(\neg X)\left(P(Y|\neg X)^2+P(\neg Y|\neg X)^2\right) - P(Y)^2 - P(\neg Y)^2 \]
Reference:
P. Tan, V. Kumar
Interestingness measures for association patterns: A perspective
In Proc. Workshop on Postprocessing in Machine Learning and Data Mining
The Gini was originally used in decision trees:
L. Breiman, J. H. Friedman, R. A. Olshen, C. J. Stone
Classification and Regression Trees

Since:

0.7.5

Author:

Frederic Sautter

Constructor Summary

Constructors
Constructor Description

GiniIndex()
Constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`double`	`measure(int t, int sX, int sY, int sXY)`	Computes the value of the measure for a given support values

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

- Constructor Detail
  - GiniIndex
```
public GiniIndex()
```
    Constructor.
- Method Detail
  - measure
```
public double measure(int t,
                      int sX,
                      int sY,
                      int sXY)
```
    Description copied from interface: InterestingnessMeasure
    
    Computes the value of the measure for a given support values
    
    Specified by:
    
    measure in interface InterestingnessMeasure
    
    Parameters:
    
    t - Total number of transaction
    
    sX - Support of the antecedent
    
    sY - Support of the consequent
    
    sXY - Support of the union of antecedent and consequent
    
    Returns:
    
    value of the measure