affinity | 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)
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