Association Rule Definitions

Definitions:

•Set of items: I={I1,I2,…,Im}

•Transactions: D={t1,t2, …, tn}, tj∈I

•Itemset: {Ii1,Ii2, …, Iik} ∈I

•Support of an itemset: Percentage of transactions which contain that itemset.

•Large (Frequent) itemset: Itemset whose number of occurrences is above a threshold.

•Association Rule (AR): implication X=>Y where X,Y ∈I and X ∩ Y = ∅;

•Support of AR (s) X  => Y: Percentage of transactions that contain X ∪ Y

•Confidence of AR (a) X => Y: Ratio of number of transactions that contain X ∪ Y to the number that contain X

 

Example:

The caculation is based on the Transacion.

Support shows the overall posibility of the apperance of the items in X and Y.

Confidence shows the possibility of the relation with the items with X and Y.