SEG 4630 Tutorial 11

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SEG 4630 Tutorial 11

• Sequential Patterns With Time Constraints
• Hints for assignment 2
• Lijun Chang

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Definition of Subsequence

• A data-sequence d contains a sequence s
  (n m), iff there exist integers l1
  u1 i n.
• If there exist a mapping from s to d satisfy all
  the constraints specified, then we will say that
  d contains s

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Widows Size constraint

• transaction-time(dui) transaction-time(dli)
  window-size, 1 i n
• ws 1, d
• s1 , Yes
• s2 , Yes
• s3 , Yes

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Max Span constraint

• transaction-time(dun) transaction-time(dl1)
  max-span
• maxspan 2, d
• s1 , Yes
• s2 , Yes
• s3 , Yes

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Min Gap constraint

• transaction-time(dli) transaction-time(du(i-1))
  min-gap, 2 i n
• mingap 1, d
• s1 , No
• s2 , Yes
• s3 , Yes

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Max Gap constraint

• transaction-time(dui) transaction-time(dl(i-1))
  max-gap, 2 i n
• maxgap 2, d
• s1 , Yes
• s2 , Yes
• s3 , Yes

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Examples

• Q.12(p.480)
• For each of the sequence w
  below,
• determine whether they are subsequences of the
  following data sequence
• s A,BC,DA,BC,DA,BC,D
• subjected to the following timing constraints
• mingap 0 (interval between last event in ei
  and first event in ei1 is 0)
• maxgap 2 (interval between first event in ei
  and last event in ei1 is 2)
• maxspan 6 (interval between first event in e1
  and last event in elast is 6)
• ws 1 (time between first and last events in ei
  is 1)

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More Examples

• s
• w

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More Examples

• s
• w

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Hints for ass2

• Q1(a), Find all frequent itemsets (up to size 4)
• Apriori algorithm (Lecture notes Ch6 p15)
• All items in an itemset must be ordered
• Frequent 3-itemsets 1,2,3, 1,2,4,
  2,3,4,2,4,5
• Candidate 4-itemsets 1,2,3,4
• After prune None

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Hints for ass2

• Q1(b), Find all association rules using frequent
  4-itemsets
• Apriori algorithm (Lecture notes Ch6 p27-30)
• enumerate it can generate (24-214) candidate
  association rules from a single frequent 4-itemset