affinity {arules} | R Documentation |

Provides the generic function `affinity()`

and methods to compute
and return a similarity matrix with the affinities between items for a set
itemsets stored in a matrix or in transactions via its superclass itemMatrix.

```
affinity(x)
## S4 method for signature 'matrix'
affinity(x)
## S4 method for signature 'itemMatrix'
affinity(x)
```

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

Affinity between the two items `i`

and `j`

is defined by Aggarwal et
al. (2002) as

```
A(i,j) = \frac{supp(\{i,j\})}{supp(\{i\}) + supp(\{j\}) -
supp(\{i,j\})},
```

where `supp(.)`

is the support measure. Note that affinity is equivalent to the
Jaccard similarity between items.

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

.

Michael Hahsler

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.

Other proximity classes and functions:
`dissimilarity()`

,
`predict()`

,
`proximity-classes`

```
data("Adult")
## choose a sample, calculate affinities
s <- sample(Adult, 500)
s
a <- affinity(s)
image(a)
```

[Package *arules* version 1.7-7 Index]