31-07-2012, 03:50 PM
Association Rules
association rules.ppt (Size: 1.58 MB / Downloads: 93)
Advantages:
Uses large itemset property.
Easily parallelized
Easy to implement.
Disadvantages:
Assumes transaction database is memory resident.
Requires up to m database scans.
Vertical Layout
Rather than have
Transaction ID – list of items (Transactional)
We have
Item – List of transactions (TID-list)
Now to count itemset AB
Intersect TID-list of itemA with TID-list of itemB
All data for a particular item is available
Eclat Algorithm
Dynamically process each transaction online maintaining 2-itemset counts.
Transform
Partition L2 using 1-item prefix
Equivalence classes - {AB, AC, AD}, {BC, BD}, {CD}
Transform database to vertical form
Asynchronous Phase
For each equivalence class E
Compute frequent (E)
Multiple-level Association Rules
Items often form hierarchy
Flexible support settings: Items at the lower level are expected to have lower support.
Transaction database can be encoded based on dimensions and levels
explore shared multi-level mining