affinity {arules} | R Documentation

## Computing Affinity Between Items

### Description

Provides the generic function `affinity` and the S4 methods to compute and return a similarity matrix with the affinities between items for a set of `transactions`.

### Usage

    affinity(x)

### Arguments

`x` | a matrix or an object of class `itemMatrix` or `transactions`.

### Details

Affinity between the two items i and j is defined by Aggarwal et al. (2002) as

A(i,j) = sup({i,j})/(sup({i}) + sup({j}) - sup({i,j})),

where sup(.) is the support measure. This means that affinity is the Jaccard similarity between items.

### Value

returns an object of class `ar_similarity` which represents the affinities between items in `x`.

### References

Charu C. Aggarwal, Cecilia Procopiuc, and Philip S. Yu (2002) Finding localized associations in market basket data, IEEE Trans. on Knowledge and Data Engineering, 14(1):51–62.

### See Also

`dissimilarity`, `ar_similarity-class`, `itemMatrix-class`

### Examples

    data("Adult")

    ## choose a sample, calculate affinities
    s <- sample(Adult, 500)
    s

    a <- affinity(s)
    summary(as.vector(a))

[Package arules version 0.6-3 Index]