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Data Mining: Concepts and Techniques_ Chapter 6: Mining Frequent Patterns, Association and Correlations: Basic Concepts and Methods | PPT
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Data Mining: 
Concepts and Techniques 
(3rd ed.) 
— Chapter 6 — 
Jiawei Han, Micheline Kamber, and Jian Pei 
University of Illinois at Urbana-Champaign & 
Simon Fraser University 
©2013 Han, Kamber & Pei. All rights reserved.
September 14, 2014 Data Mining: Concepts and Techniques 2
Chapter 6: Mining Frequent Patterns, Association 
and Correlations: Basic Concepts and Methods 
3 
 Basic Concepts 
 Frequent Itemset Mining Methods 
 Which Patterns Are Interesting?—Pattern 
Evaluation Methods 
 Summary
4 
What Is Frequent Pattern Analysis? 
 Frequent pattern: a pattern (a set of items, subsequences, substructures, 
etc.) that occurs frequently in a data set 
 First proposed by Agrawal, Imielinski, and Swami [AIS93] in the context 
of frequent itemsets and association rule mining 
 Motivation: Finding inherent regularities in data 
 What products were often purchased together?— Beer and diapers?! 
 What are the subsequent purchases after buying a PC? 
 What kinds of DNA are sensitive to this new drug? 
 Can we automatically classify web documents? 
 Applications 
 Basket data analysis, cross-marketing, catalog design, sale campaign 
analysis, Web log (click stream) analysis, and DNA sequence analysis.
5 
Why Is Freq. Pattern Mining Important? 
 Freq. pattern: An intrinsic and important property of 
datasets 
 Foundation for many essential data mining tasks 
 Association, correlation, and causality analysis 
 Sequential, structural (e.g., sub-graph) patterns 
 Pattern analysis in spatiotemporal, multimedia, time-series, 
and stream data 
 Classification: discriminative, frequent pattern analysis 
 Cluster analysis: frequent pattern-based clustering 
 Data warehousing: iceberg cube and cube-gradient 
 Semantic data compression: fascicles 
 Broad applications
6 
Basic Concepts: Frequent Patterns 
 itemset: A set of one or more 
items 
 k-itemset X = {x1, …, xk} 
 (absolute) support, or, support 
count of X: Frequency or 
occurrence of an itemset X 
 (relative) support, s, is the 
fraction of transactions that 
contains X (i.e., the probability 
that a transaction contains X) 
 An itemset X is frequent if X’s 
support is no less than a minsup 
threshold 
Tid Items bought 
10 Beer, Nuts, Diaper 
20 Beer, Coffee, Diaper 
30 Beer, Diaper, Eggs 
40 Nuts, Eggs, Milk 
50 Nuts, Coffee, Diaper, Eggs, Milk 
Customer 
buys diaper 
Customer 
buys both 
Customer 
buys beer
7 
Basic Concepts: Association Rules 
 Find all the rules X  Y with 
minimum support and confidence 
 support, s, probability that a 
transaction contains X  Y 
 confidence, c, conditional 
probability that a transaction 
having X also contains Y 
Let minsup = 50%, minconf = 50% 
Freq. Pat.: Beer:3, Nuts:3, Diaper:4, Eggs:3, 
{Beer, Diaper}:3 
Tid Items bought 
10 Beer, Nuts, Diaper 
20 Beer, Coffee, Diaper 
30 Beer, Diaper, Eggs 
40 Nuts, Eggs, Milk 
50 Nuts, Coffee, Diaper, Eggs, Milk 
Customer 
buys 
diaper 
Customer 
buys both 
Customer 
buys beer 
 Association rules: (many more!) 
 Beer  Diaper (60%, 100%) 
 Diaper  Beer (60%, 75%)
8 
Closed Patterns and Max-Patterns 
 A long pattern contains a combinatorial number of sub-patterns, 
e.g., {a1, …, a100} contains (100 
1) + (100 
2) + … + 
(1 
1 
0 
0 
0 
0) = 2100 – 1 = 1.27*1030 sub-patterns! 
 Solution: Mine closed patterns and max-patterns instead 
 An itemset X is closed if X is frequent and there exists no 
super-pattern Y כ X, with the same support as X 
(proposed by Pasquier, et al. @ ICDT’99) 
 An itemset X is a max-pattern if X is frequent and there 
exists no frequent super-pattern Y כ X (proposed by 
Bayardo @ SIGMOD’98) 
 Closed pattern is a lossless compression of freq. patterns 
 Reducing the # of patterns and rules
9 
Closed Patterns and Max-Patterns 
 Exercise: Suppose a DB contains only two transactions 
 <a1, …, a100>, <a1, …, a50> 
 Let min_sup = 1 
 What is the set of closed itemset? 
 {a1, …, a100}: 1 
 {a1, …, a50}: 2 
 What is the set of max-pattern? 
 {a1, …, a100}: 1 
 What is the set of all patterns? 
 {a1}: 2, …, {a1, a2}: 2, …, {a1, a51}: 1, …, {a1, a2, …, a100}: 1 
 A big number: 2100 - 1? Why?
Chapter 5: Mining Frequent Patterns, Association 
and Correlations: Basic Concepts and Methods 
10 
 Basic Concepts 
 Frequent Itemset Mining Methods 
 Which Patterns Are Interesting?—Pattern 
Evaluation Methods 
 Summary
Scalable Frequent Itemset Mining Methods 
11 
 Apriori: A Candidate Generation-and-Test 
Approach 
 Improving the Efficiency of Apriori 
 FPGrowth: A Frequent Pattern-Growth Approach 
 ECLAT: Frequent Pattern Mining with Vertical 
Data Format
12 
The Downward Closure Property and Scalable 
Mining Methods 
 The downward closure property of frequent patterns 
 Any subset of a frequent itemset must be frequent 
 If {beer, diaper, nuts} is frequent, so is {beer, 
diaper} 
 i.e., every transaction having {beer, diaper, nuts} also 
contains {beer, diaper} 
 Scalable mining methods: Three major approaches 
 Apriori (Agrawal & Srikant@VLDB’94) 
 Freq. pattern growth (FPgrowth—Han, Pei & Yin 
@SIGMOD’00) 
 Vertical data format approach (Charm—Zaki & Hsiao 
@SDM’02)
Apriori: A Candidate Generation & Test Approach 
13 
 Apriori pruning principle: If there is any itemset which is 
infrequent, its superset should not be generated/tested! 
(Agrawal & Srikant @VLDB’94, Mannila, et al. @ KDD’ 94) 
 Method: 
 Initially, scan DB once to get frequent 1-itemset 
 Generate length (k+1) candidate itemsets from length k 
frequent itemsets 
 Test the candidates against DB 
 Terminate when no frequent or candidate set can be 
generated
14 
The Apriori Algorithm—An Example 
Database TDB 
C1 
1st scan 
L1 
Tid Items 
10 A, C, D 
20 B, C, E 
30 A, B, C, E 
40 B, E 
L2 
Itemset sup 
{A} 2 
{B} 3 
{C} 3 
{D} 1 
{E} 3 
C2 C2 
2nd scan 
C3 3rd scan L3 
Itemset sup 
{A} 2 
{B} 3 
{C} 3 
{E} 3 
Itemset 
{A, B} 
{A, C} 
{A, E} 
{B, C} 
{B, E} 
{C, E} 
Itemset sup 
{A, B} 1 
{A, C} 2 
{A, E} 1 
{B, C} 2 
{B, E} 3 
{C, E} 2 
Itemset sup 
{A, C} 2 
{B, C} 2 
{B, E} 3 
{C, E} 2 
Itemset 
{B, C, E} 
Itemset sup 
{B, C, E} 2 
Supmin = 2
15 
The Apriori Algorithm (Pseudo-Code) 
Ck: Candidate itemset of size k 
Lk : frequent itemset of size k 
L1 = {frequent items}; 
for (k = 1; Lk !=; k++) do begin 
Ck+1 = candidates generated from Lk; 
for each transaction t in database do 
increment the count of all candidates in Ck+1 that 
are contained in t 
Lk+1 = candidates in Ck+1 with min_support 
end 
return k Lk;
16 
Implementation of Apriori 
 How to generate candidates? 
 Step 1: self-joining Lk 
 Step 2: pruning 
 Example of Candidate-generation 
 L3={abc, abd, acd, ace, bcd} 
 Self-joining: L3*L3 
 abcd from abc and abd 
 acde from acd and ace 
 Pruning: 
 acde is removed because ade is not in L3 
 C4 = {abcd}
19 
Candidate Generation: An SQL Implementation 
 SQL Implementation of candidate generation 
 Suppose the items in Lk-1 are listed in an order 
 Step 1: self-joining Lk-1 
insert into Ck 
select p.item1, p.item2, …, p.itemk-1, q.itemk-1 
from Lk-1 p, Lk-1 q 
where p.item1=q.item1, …, p.itemk-2=q.itemk-2, p.itemk-1 < 
q.itemk-1 
 Step 2: pruning 
forall itemsets c in Ck do 
forall (k-1)-subsets s of c do 
if (s is not in Lk-1) then delete c from Ck 
 Use object-relational extensions like UDFs, BLOBs, and Table functions for 
efficient implementation [S. Sarawagi, S. Thomas, and R. Agrawal. Integrating 
association rule mining with relational database systems: Alternatives and 
implications. SIGMOD’98]
Scalable Frequent Itemset Mining Methods 
20 
 Apriori: A Candidate Generation-and-Test Approach 
 Improving the Efficiency of Apriori 
 FPGrowth: A Frequent Pattern-Growth Approach 
 ECLAT: Frequent Pattern Mining with Vertical Data Format 
 Mining Close Frequent Patterns and Maxpatterns
21 
Further Improvement of the Apriori Method 
 Major computational challenges 
 Multiple scans of transaction database 
 Huge number of candidates 
 Tedious workload of support counting for candidates 
 Improving Apriori: general ideas 
 Reduce passes of transaction database scans 
 Shrink number of candidates 
 Facilitate support counting of candidates
Partition: Scan Database Only Twice 
 Any itemset that is potentially frequent in DB must be 
frequent in at least one of the partitions of DB 
 Scan 1: partition database and find local frequent 
patterns 
 Scan 2: consolidate global frequent patterns 
 A. Savasere, E. Omiecinski and S. Navathe, VLDB’95 
DB1 + DB2 + + DBk = DB 
sup1(i) < σDB1 sup2(i) < σDB2 supk(i) < σDBk sup(i) < σDB
23 
DHP: Reduce the Number of Candidates 
 A k-itemset whose corresponding hashing bucket count is below the 
threshold cannot be frequent 
 Candidates: a, b, c, d, e 
 Hash entries 
 {ab, ad, ae} 
 {bd, be, de} 
 … 
 Frequent 1-itemset: a, b, d, e 
. 
. 
. 
 ab is not a candidate 2-itemset if the sum of count of {ab, ad, ae} 
is below support threshold 
 J. Park, M. Chen, and P. Yu. An effective hash-based algorithm for 
mining association rules. SIGMOD’95 
count itemsets 
35 {ab, ad, ae} 
{yz, qs, wt} 
88 
102 
{bd, be, de} 
. 
. 
. 
Hash Table
24 
Sampling for Frequent Patterns 
 Select a sample of original database, mine frequent 
patterns within sample using Apriori 
 Scan database once to verify frequent itemsets found in 
sample, only borders of closure of frequent patterns are 
checked 
 Example: check abcd instead of ab, ac, …, etc. 
 Scan database again to find missed frequent patterns 
 H. Toivonen. Sampling large databases for association 
rules. In VLDB’96
25 
DIC: Reduce Number of Scans 
ABCD 
ABC ABD ACD BCD 
AB AC BC AD BD CD 
A B C D 
{} 
Itemset lattice 
 Once both A and D are determined 
frequent, the counting of AD begins 
 Once all length-2 subsets of BCD are 
determined frequent, the counting of BCD 
begins 
Transactions 
1-itemsets 
2-itemsets 
… 
Apriori 
1-itemsets 
2-items 
DIC 3-items 
S. Brin R. Motwani, J. Ullman, 
and S. Tsur. Dynamic itemset 
counting and implication rules for 
market basket data. In 
SIGMOD’97
Scalable Frequent Itemset Mining Methods 
26 
 Apriori: A Candidate Generation-and-Test Approach 
 Improving the Efficiency of Apriori 
 FPGrowth: A Frequent Pattern-Growth Approach 
 ECLAT: Frequent Pattern Mining with Vertical Data Format 
 Mining Close Frequent Patterns and Maxpatterns
27 
Pattern-Growth Approach: Mining Frequent 
Patterns Without Candidate Generation 
 Bottlenecks of the Apriori approach 
 Breadth-first (i.e., level-wise) search 
 Candidate generation and test 
 Often generates a huge number of candidates 
 The FPGrowth Approach (J. Han, J. Pei, and Y. Yin, SIGMOD’ 00) 
 Depth-first search 
 Avoid explicit candidate generation 
 Major philosophy: Grow long patterns from short ones using local 
frequent items only 
 “abc” is a frequent pattern 
 Get all transactions having “abc”, i.e., project DB on abc: DB|abc 
 “d” is a local frequent item in DB|abc  abcd is a frequent pattern
28 
Construct FP-tree from a Transaction Database 
{} 
f:4 c:1 
b:1 
p:1 
c:3 b:1 
a:3 
m:2 b:1 
p:2 m:1 
Header Table 
Item frequency head 
f 4 
c 4 
a 3 
b 3 
m 3 
p 3 
min_support = 3 
TID Items bought (ordered) frequent items 
100 {f, a, c, d, g, i, m, p} {f, c, a, m, p} 
200 {a, b, c, f, l, m, o} {f, c, a, b, m} 
300 {b, f, h, j, o, w} {f, b} 
400 {b, c, k, s, p} {c, b, p} 
500 {a, f, c, e, l, p, m, n} {f, c, a, m, p} 
1. Scan DB once, find 
frequent 1-itemset (single 
item pattern) 
2. Sort frequent items in 
frequency descending 
order, f-list 
3. Scan DB again, construct 
FP-tree 
F-list = f-c-a-b-m-p
29 
Partition Patterns and Databases 
 Frequent patterns can be partitioned into subsets 
according to f-list 
 F-list = f-c-a-b-m-p 
 Patterns containing p 
 Patterns having m but no p 
 … 
 Patterns having c but no a nor b, m, p 
 Pattern f 
 Completeness and non-redundency
30 
Find Patterns Having P From P-conditional Database 
 Starting at the frequent item header table in the FP-tree 
 Traverse the FP-tree by following the link of each frequent item p 
 Accumulate all of transformed prefix paths of item p to form p’s 
conditional pattern base 
Conditional pattern bases 
item cond. pattern base 
c f:3 
a fc:3 
b fca:1, f:1, c:1 
m fca:2, fcab:1 
p fcam:2, cb:1 
{} 
f:4 c:1 
b:1 
p:1 
c:3 b:1 
a:3 
m:2 b:1 
p:2 m:1 
Header Table 
Item frequency head 
f 4 
c 4 
a 3 
b 3 
m 3 
p 3
From Conditional Pattern-bases to Conditional FP-trees 
All frequent 
patterns relate to m 
m, 
fm, cm, am, 
fcm, fam, cam, 
fcam 
31 
 For each pattern-base 
 Accumulate the count for each item in the base 
 Construct the FP-tree for the frequent items of the 
pattern base 
m-conditional pattern base: 
fca:2, fcab:1 
{} 
f:3 
c:3 
a:3 
 
 
m-conditional FP-tree 
{} 
f:4 c:1 
b:1 
p:1 
c:3 b:1 
a:3 
m:2 b:1 
p:2 m:1 
Header Table 
Item frequency head 
f 4 
c 4 
a 3 
b 3 
m 3 
p 3
32 
Recursion: Mining Each Conditional FP-tree 
{} 
f:3 
c:3 
a:3 
Cond. pattern base of “am”: (fc:3) 
m-conditional FP-tree 
{} 
f:3 
c:3 
am-conditional FP-tree 
Cond. pattern base of “cm”: (f:3) 
{} 
f:3 
cm-conditional FP-tree 
Cond. pattern base of “cam”: (f:3) 
{} 
f:3 
cam-conditional FP-tree
33 
A Special Case: Single Prefix Path in FP-tree 
 Suppose a (conditional) FP-tree T has a shared 
single prefix-path P 
 Mining can be decomposed into two parts 
 Reduction of the single prefix path into one node 
 Concatenation of the mining results of the two 
parts 
 
{} 
a1:n1 
a2:n2 
a3:n3 
b1:m1 
C1:k1 
C2:k2 C3:k3 
r1 
b1:m1 
C1:k1 
C2:k2 C3:k3 
+ 
{} 
a1:n1 
a2:n2 
a3:n3 
r1 =
34 
Benefits of the FP-tree Structure 
 Completeness 
 Preserve complete information for frequent pattern 
mining 
 Never break a long pattern of any transaction 
 Compactness 
 Reduce irrelevant info—infrequent items are gone 
 Items in frequency descending order: the more 
frequently occurring, the more likely to be shared 
 Never be larger than the original database (not count 
node-links and the count field)
35 
The Frequent Pattern Growth Mining Method 
 Idea: Frequent pattern growth 
 Recursively grow frequent patterns by pattern and 
database partition 
 Method 
 For each frequent item, construct its conditional 
pattern-base, and then its conditional FP-tree 
 Repeat the process on each newly created conditional 
FP-tree 
 Until the resulting FP-tree is empty, or it contains only 
one path—single path will generate all the 
combinations of its sub-paths, each of which is a 
frequent pattern
36 
Scaling FP-growth by Database Projection 
 What about if FP-tree cannot fit in memory? 
 DB projection 
 First partition a database into a set of projected DBs 
 Then construct and mine FP-tree for each projected DB 
 Parallel projection vs. partition projection techniques 
 Parallel projection 
 Project the DB in parallel for each frequent item 
 Parallel projection is space costly 
 All the partitions can be processed in parallel 
 Partition projection 
 Partition the DB based on the ordered frequent items 
 Passing the unprocessed parts to the subsequent partitions
37 
Partition-Based Projection 
 Parallel projection needs a lot 
of disk space 
 Partition projection saves it 
Tran. DB 
fcamp 
fcabm 
fb 
cbp 
fcamp 
p-proj DB 
fcam 
cb 
fcam 
m-proj DB 
fcab 
fca 
fca 
b-proj DB 
f 
cb 
… 
a-proj DB 
fc 
… 
c-proj DB 
f 
… 
f-proj DB 
… 
am-proj DB 
fc 
fc 
fc 
cm-proj DB 
f 
f 
f 
…
38 
FP-Growth vs. Apriori: Scalability With the Support 
Threshold 
100 
90 
80 
70 
60 
50 
40 
30 
20 
10 
0 
Data set T25I20D10K 
0 0.5 1 1.5 2 2.5 3 
Support threshold(%) 
Run time(sec.) 
D1 FP-grow th runtime 
D1 Apriori runtime
FP-Growth vs. Tree-Projection: Scalability with 
the Support Threshold 
Data Mining: Concepts and Techniques 39 
140 
120 
100 
80 
60 
40 
20 
0 
0 0.5 1 1.5 2 
Support threshold (%) 
Runtime (sec.) 
D2 FP-growth 
D2 TreeProjection 
Data set T25I20D100K
40 
Advantages of the Pattern Growth Approach 
 Divide-and-conquer: 
 Decompose both the mining task and DB according to the 
frequent patterns obtained so far 
 Lead to focused search of smaller databases 
 Other factors 
 No candidate generation, no candidate test 
 Compressed database: FP-tree structure 
 No repeated scan of entire database 
 Basic ops: counting local freq items and building sub FP-tree, no 
pattern search and matching 
 A good open-source implementation and refinement of FPGrowth 
 FPGrowth+ (Grahne and J. Zhu, FIMI'03)
41 
Further Improvements of Mining Methods 
 AFOPT (Liu, et al. @ KDD’03) 
 A “push-right” method for mining condensed frequent pattern 
(CFP) tree 
 Carpenter (Pan, et al. @ KDD’03) 
 Mine data sets with small rows but numerous columns 
 Construct a row-enumeration tree for efficient mining 
 FPgrowth+ (Grahne and Zhu, FIMI’03) 
 Efficiently Using Prefix-Trees in Mining Frequent Itemsets, Proc. 
ICDM'03 Int. Workshop on Frequent Itemset Mining 
Implementations (FIMI'03), Melbourne, FL, Nov. 2003 
 TD-Close (Liu, et al, SDM’06)
Extension of Pattern Growth Mining Methodology 
42 
 Mining closed frequent itemsets and max-patterns 
 CLOSET (DMKD’00), FPclose, and FPMax (Grahne & Zhu, Fimi’03) 
 Mining sequential patterns 
 PrefixSpan (ICDE’01), CloSpan (SDM’03), BIDE (ICDE’04) 
 Mining graph patterns 
 gSpan (ICDM’02), CloseGraph (KDD’03) 
 Constraint-based mining of frequent patterns 
 Convertible constraints (ICDE’01), gPrune (PAKDD’03) 
 Computing iceberg data cubes with complex measures 
 H-tree, H-cubing, and Star-cubing (SIGMOD’01, VLDB’03) 
 Pattern-growth-based Clustering 
 MaPle (Pei, et al., ICDM’03) 
 Pattern-Growth-Based Classification 
 Mining frequent and discriminative patterns (Cheng, et al, ICDE’07)
Scalable Frequent Itemset Mining Methods 
43 
 Apriori: A Candidate Generation-and-Test Approach 
 Improving the Efficiency of Apriori 
 FPGrowth: A Frequent Pattern-Growth Approach 
 ECLAT: Frequent Pattern Mining with Vertical Data Format 
 Mining Close Frequent Patterns and Maxpatterns
ECLAT: Mining by Exploring Vertical Data Format 
44 
 Vertical format: t(AB) = {T11, T25, …} 
 tid-list: list of trans.-ids containing an itemset 
 Deriving frequent patterns based on vertical intersections 
 t(X) = t(Y): X and Y always happen together 
 t(X)  t(Y): transaction having X always has Y 
 Using diffset to accelerate mining 
 Only keep track of differences of tids 
 t(X) = {T1, T2, T3}, t(XY) = {T1, T3} 
 Diffset (XY, X) = {T2} 
 Eclat (Zaki et al. @KDD’97) 
 Mining Closed patterns using vertical format: CHARM (Zaki & 
Hsiao@SDM’02)
Scalable Frequent Itemset Mining Methods 
45 
 Apriori: A Candidate Generation-and-Test Approach 
 Improving the Efficiency of Apriori 
 FPGrowth: A Frequent Pattern-Growth Approach 
 ECLAT: Frequent Pattern Mining with Vertical Data Format 
 Mining Close Frequent Patterns and Maxpatterns
Mining Frequent Closed Patterns: CLOSET 
 Flist: list of all frequent items in support ascending order 
 Flist: d-a-f-e-c 
 Divide search space 
 Patterns having d 
 Patterns having d but no a, etc. 
 Find frequent closed pattern recursively 
Min_sup=2 
 Every transaction having d also has cfa  cfad is a 
frequent closed pattern 
 J. Pei, J. Han & R. Mao. “CLOSET: An Efficient Algorithm for 
Mining Frequent Closed Itemsets", DMKD'00. 
TID Items 
10 a, c, d, e, f 
20 a, b, e 
30 c, e, f 
40 a, c, d, f 
50 c, e, f
CLOSET+: Mining Closed Itemsets by Pattern-Growth 
 Itemset merging: if Y appears in every occurrence of X, then Y 
is merged with X 
 Sub-itemset pruning: if Y כ X, and sup(X) = sup(Y), X and all of 
X’s descendants in the set enumeration tree can be pruned 
 Hybrid tree projection 
 Bottom-up physical tree-projection 
 Top-down pseudo tree-projection 
 Item skipping: if a local frequent item has the same support in 
several header tables at different levels, one can prune it from 
the header table at higher levels 
 Efficient subset checking
MaxMiner: Mining Max-Patterns 
 1st scan: find frequent items 
 A, B, C, D, E 
 2nd scan: find support for 
 AB, AC, AD, AE, ABCDE 
 BC, BD, BE, BCDE 
 CD, CE, CDE, DE 
 Since BCDE is a max-pattern, no need to check BCD, BDE, 
CDE in later scan 
 R. Bayardo. Efficiently mining long patterns from 
databases. SIGMOD’98 
Tid Items 
10 A, B, C, D, E 
20 B, C, D, E, 
30 A, C, D, F 
Potential 
max-patterns
CHARM: Mining by Exploring Vertical Data 
Format 
 Vertical format: t(AB) = {T11, T25, …} 
 tid-list: list of trans.-ids containing an itemset 
 Deriving closed patterns based on vertical intersections 
 t(X) = t(Y): X and Y always happen together 
 t(X)  t(Y): transaction having X always has Y 
 Using diffset to accelerate mining 
 Only keep track of differences of tids 
 t(X) = {T1, T2, T3}, t(XY) = {T1, T3} 
 Diffset (XY, X) = {T2} 
 Eclat/MaxEclat (Zaki et al. @KDD’97), VIPER(P. Shenoy et 
al.@SIGMOD’00), CHARM (Zaki & Hsiao@SDM’02)
50 
Visualization of Association Rules: Plane Graph
51 
Visualization of Association Rules: Rule Graph
52 
Visualization of Association Rules 
(SGI/MineSet 3.0)
53 
Computational Complexity of Frequent Itemset 
Mining 
 How many itemsets are potentially to be generated in the worst case? 
 The number of frequent itemsets to be generated is senstive to the 
minsup threshold 
 When minsup is low, there exist potentially an exponential number of 
frequent itemsets 
 The worst case: MN where M: # distinct items, and N: max length of 
transactions 
 The worst case complexty vs. the expected probability 
 Ex. Suppose Walmart has 104 kinds of products 
 The chance to pick up one product 10-4 
 The chance to pick up a particular set of 10 products: ~10-40 
 What is the chance this particular set of 10 products to be frequent 
103 times in 109 transactions?
Chapter 5: Mining Frequent Patterns, Association 
and Correlations: Basic Concepts and Methods 
54 
 Basic Concepts 
 Frequent Itemset Mining Methods 
 Which Patterns Are Interesting?—Pattern 
Evaluation Methods 
 Summary
55 
Interestingness Measure: Correlations (Lift) 
 play basketball  eat cereal [40%, 66.7%] is misleading 
 The overall % of students eating cereal is 75% > 66.7%. 
 play basketball  not eat cereal [20%, 33.3%] is more accurate, 
although with lower support and confidence 
 Measure of dependent/correlated events: lift 
0.89 
P A B 
( ) 
P A P B 
2000/ 5000 
lif t(B,C)   
3000/ 5000*3750/ 5000 
Basketball Not basketball Sum (row) 
Cereal 2000 1750 3750 
Not cereal 1000 250 1250 
Sum(col.) 3000 2000 5000 
( ) ( ) 
lift 
 
 
1.33 
1000/ 5000 
lif t(B,C)   
3000/ 5000*1250/ 5000
56 
Are lift and 2 Good Measures of Correlation? 
 “Buy walnuts  buy 
milk [1%, 80%]” is 
misleading if 85% of 
customers buy milk 
 Support and confidence 
are not good to indicate 
correlations 
 Over 20 interestingness 
measures have been 
proposed (see Tan, 
Kumar, Sritastava 
@KDD’02) 
 Which are good ones?
57 
Null-Invariant Measures
Comparison of Interestingness Measures 
 Null-(transaction) invariance is crucial for correlation analysis 
 Lift and 2 are not null-invariant 
 5 null-invariant measures 
Milk No Milk Sum (row) 
Coffee m, c ~m, c c 
No Coffee m, ~c ~m, ~c ~c 
Sum(col.) m ~m  
Kulczynski 
measure (1927) 
Null-transactions 
w.r.t. m and c Null-invariant 
Subtle: They disagree 
September 14, 2014 Data Mining: Concepts and Techniques 58
59 
Analysis of DBLP Coauthor Relationships 
Recent DB conferences, removing balanced associations, low sup, etc. 
Advisor-advisee relation: Kulc: high, 
coherence: low, cosine: middle 
 Tianyi Wu, Yuguo Chen and Jiawei Han, “Association Mining in Large 
Databases: A Re-Examination of Its Measures”, Proc. 2007 Int. Conf. 
Principles and Practice of Knowledge Discovery in Databases 
(PKDD'07), Sept. 2007
Which Null-Invariant Measure Is Better? 
 IR (Imbalance Ratio): measure the imbalance of two 
itemsets A and B in rule implications 
 Kulczynski and Imbalance Ratio (IR) together present a 
clear picture for all the three datasets D4 through D6 
 D4 is balanced & neutral 
 D5 is imbalanced & neutral 
 D6 is very imbalanced & neutral
Chapter 5: Mining Frequent Patterns, Association 
and Correlations: Basic Concepts and Methods 
61 
 Basic Concepts 
 Frequent Itemset Mining Methods 
 Which Patterns Are Interesting?—Pattern 
Evaluation Methods 
 Summary
62 
Summary 
 Basic concepts: association rules, support-confident 
framework, closed and max-patterns 
 Scalable frequent pattern mining methods 
 Apriori (Candidate generation & test) 
 Projection-based (FPgrowth, CLOSET+, ...) 
 Vertical format approach (ECLAT, CHARM, ...) 
 Which patterns are interesting? 
 Pattern evaluation methods
September 14, 2014 Data Mining: Concepts and Techniques 63
64 
Ref: Basic Concepts of Frequent Pattern Mining 
 (Association Rules) R. Agrawal, T. Imielinski, and A. Swami. Mining 
association rules between sets of items in large databases. 
SIGMOD'93. 
 (Max-pattern) R. J. Bayardo. Efficiently mining long patterns from 
databases. SIGMOD'98. 
 (Closed-pattern) N. Pasquier, Y. Bastide, R. Taouil, and L. Lakhal. 
Discovering frequent closed itemsets for association rules. ICDT'99. 
 (Sequential pattern) R. Agrawal and R. Srikant. Mining sequential 
patterns. ICDE'95
65 
Ref: Apriori and Its Improvements 
 R. Agrawal and R. Srikant. Fast algorithms for mining association rules. 
VLDB'94. 
 H. Mannila, H. Toivonen, and A. I. Verkamo. Efficient algorithms for 
discovering association rules. KDD'94. 
 A. Savasere, E. Omiecinski, and S. Navathe. An efficient algorithm for 
mining association rules in large databases. VLDB'95. 
 J. S. Park, M. S. Chen, and P. S. Yu. An effective hash-based algorithm 
for mining association rules. SIGMOD'95. 
 H. Toivonen. Sampling large databases for association rules. VLDB'96. 
 S. Brin, R. Motwani, J. D. Ullman, and S. Tsur. Dynamic itemset 
counting and implication rules for market basket analysis. SIGMOD'97. 
 S. Sarawagi, S. Thomas, and R. Agrawal. Integrating association rule 
mining with relational database systems: Alternatives and implications. 
SIGMOD'98.
66 
Ref: Depth-First, Projection-Based FP Mining 
 R. Agarwal, C. Aggarwal, and V. V. V. Prasad. A tree projection algorithm for 
generation of frequent itemsets. J. Parallel and Distributed Computing:02. 
 J. Han, J. Pei, and Y. Yin. Mining frequent patterns without candidate 
generation. SIGMOD’ 00. 
 J. Liu, Y. Pan, K. Wang, and J. Han. Mining Frequent Item Sets by 
Opportunistic Projection. KDD'02. 
 J. Han, J. Wang, Y. Lu, and P. Tzvetkov. Mining Top-K Frequent Closed 
Patterns without Minimum Support. ICDM'02. 
 J. Wang, J. Han, and J. Pei. CLOSET+: Searching for the Best Strategies for 
Mining Frequent Closed Itemsets. KDD'03. 
 G. Liu, H. Lu, W. Lou, J. X. Yu. On Computing, Storing and Querying Frequent 
Patterns. KDD'03. 
 G. Grahne and J. Zhu, Efficiently Using Prefix-Trees in Mining Frequent 
Itemsets, Proc. ICDM'03 Int. Workshop on Frequent Itemset Mining 
Implementations (FIMI'03), Melbourne, FL, Nov. 2003
67 
Ref: Vertical Format and Row Enumeration Methods 
 M. J. Zaki, S. Parthasarathy, M. Ogihara, and W. Li. Parallel algorithm 
for discovery of association rules. DAMI:97. 
 Zaki and Hsiao. CHARM: An Efficient Algorithm for Closed Itemset 
Mining, SDM'02. 
 C. Bucila, J. Gehrke, D. Kifer, and W. White. DualMiner: A Dual- 
Pruning Algorithm for Itemsets with Constraints. KDD’02. 
 F. Pan, G. Cong, A. K. H. Tung, J. Yang, and M. Zaki , CARPENTER: 
Finding Closed Patterns in Long Biological Datasets. KDD'03. 
 H. Liu, J. Han, D. Xin, and Z. Shao, Mining Interesting Patterns from 
Very High Dimensional Data: A Top-Down Row Enumeration 
Approach, SDM'06.
68 
Ref: Mining Correlations and Interesting Rules 
 M. Klemettinen, H. Mannila, P. Ronkainen, H. Toivonen, and A. I. 
Verkamo. Finding interesting rules from large sets of discovered 
association rules. CIKM'94. 
 S. Brin, R. Motwani, and C. Silverstein. Beyond market basket: 
Generalizing association rules to correlations. SIGMOD'97. 
 C. Silverstein, S. Brin, R. Motwani, and J. Ullman. Scalable 
techniques for mining causal structures. VLDB'98. 
 P.-N. Tan, V. Kumar, and J. Srivastava. Selecting the Right 
Interestingness Measure for Association Patterns. KDD'02. 
 E. Omiecinski. Alternative Interest Measures for Mining 
Associations. TKDE’03. 
 T. Wu, Y. Chen and J. Han, “Association Mining in Large Databases: 
A Re-Examination of Its Measures”, PKDD'07
69 
Ref: Freq. Pattern Mining Applications 
 Y. Huhtala, J. Kärkkäinen, P. Porkka, H. Toivonen. Efficient 
Discovery of Functional and Approximate Dependencies Using 
Partitions. ICDE’98. 
 H. V. Jagadish, J. Madar, and R. Ng. Semantic Compression and 
Pattern Extraction with Fascicles. VLDB'99. 
 T. Dasu, T. Johnson, S. Muthukrishnan, and V. Shkapenyuk. 
Mining Database Structure; or How to Build a Data Quality 
Browser. SIGMOD'02. 
 K. Wang, S. Zhou, J. Han. Profit Mining: From Patterns to Actions. 
EDBT’02.

Data Mining: Concepts and Techniques_ Chapter 6: Mining Frequent Patterns, Association and Correlations: Basic Concepts and Methods

  • 1.
    1 Data Mining: Concepts and Techniques (3rd ed.) — Chapter 6 — Jiawei Han, Micheline Kamber, and Jian Pei University of Illinois at Urbana-Champaign & Simon Fraser University ©2013 Han, Kamber & Pei. All rights reserved.
  • 2.
    September 14, 2014Data Mining: Concepts and Techniques 2
  • 3.
    Chapter 6: MiningFrequent Patterns, Association and Correlations: Basic Concepts and Methods 3  Basic Concepts  Frequent Itemset Mining Methods  Which Patterns Are Interesting?—Pattern Evaluation Methods  Summary
  • 4.
    4 What IsFrequent Pattern Analysis?  Frequent pattern: a pattern (a set of items, subsequences, substructures, etc.) that occurs frequently in a data set  First proposed by Agrawal, Imielinski, and Swami [AIS93] in the context of frequent itemsets and association rule mining  Motivation: Finding inherent regularities in data  What products were often purchased together?— Beer and diapers?!  What are the subsequent purchases after buying a PC?  What kinds of DNA are sensitive to this new drug?  Can we automatically classify web documents?  Applications  Basket data analysis, cross-marketing, catalog design, sale campaign analysis, Web log (click stream) analysis, and DNA sequence analysis.
  • 5.
    5 Why IsFreq. Pattern Mining Important?  Freq. pattern: An intrinsic and important property of datasets  Foundation for many essential data mining tasks  Association, correlation, and causality analysis  Sequential, structural (e.g., sub-graph) patterns  Pattern analysis in spatiotemporal, multimedia, time-series, and stream data  Classification: discriminative, frequent pattern analysis  Cluster analysis: frequent pattern-based clustering  Data warehousing: iceberg cube and cube-gradient  Semantic data compression: fascicles  Broad applications
  • 6.
    6 Basic Concepts:Frequent Patterns  itemset: A set of one or more items  k-itemset X = {x1, …, xk}  (absolute) support, or, support count of X: Frequency or occurrence of an itemset X  (relative) support, s, is the fraction of transactions that contains X (i.e., the probability that a transaction contains X)  An itemset X is frequent if X’s support is no less than a minsup threshold Tid Items bought 10 Beer, Nuts, Diaper 20 Beer, Coffee, Diaper 30 Beer, Diaper, Eggs 40 Nuts, Eggs, Milk 50 Nuts, Coffee, Diaper, Eggs, Milk Customer buys diaper Customer buys both Customer buys beer
  • 7.
    7 Basic Concepts:Association Rules  Find all the rules X  Y with minimum support and confidence  support, s, probability that a transaction contains X  Y  confidence, c, conditional probability that a transaction having X also contains Y Let minsup = 50%, minconf = 50% Freq. Pat.: Beer:3, Nuts:3, Diaper:4, Eggs:3, {Beer, Diaper}:3 Tid Items bought 10 Beer, Nuts, Diaper 20 Beer, Coffee, Diaper 30 Beer, Diaper, Eggs 40 Nuts, Eggs, Milk 50 Nuts, Coffee, Diaper, Eggs, Milk Customer buys diaper Customer buys both Customer buys beer  Association rules: (many more!)  Beer  Diaper (60%, 100%)  Diaper  Beer (60%, 75%)
  • 8.
    8 Closed Patternsand Max-Patterns  A long pattern contains a combinatorial number of sub-patterns, e.g., {a1, …, a100} contains (100 1) + (100 2) + … + (1 1 0 0 0 0) = 2100 – 1 = 1.27*1030 sub-patterns!  Solution: Mine closed patterns and max-patterns instead  An itemset X is closed if X is frequent and there exists no super-pattern Y כ X, with the same support as X (proposed by Pasquier, et al. @ ICDT’99)  An itemset X is a max-pattern if X is frequent and there exists no frequent super-pattern Y כ X (proposed by Bayardo @ SIGMOD’98)  Closed pattern is a lossless compression of freq. patterns  Reducing the # of patterns and rules
  • 9.
    9 Closed Patternsand Max-Patterns  Exercise: Suppose a DB contains only two transactions  <a1, …, a100>, <a1, …, a50>  Let min_sup = 1  What is the set of closed itemset?  {a1, …, a100}: 1  {a1, …, a50}: 2  What is the set of max-pattern?  {a1, …, a100}: 1  What is the set of all patterns?  {a1}: 2, …, {a1, a2}: 2, …, {a1, a51}: 1, …, {a1, a2, …, a100}: 1  A big number: 2100 - 1? Why?
  • 10.
    Chapter 5: MiningFrequent Patterns, Association and Correlations: Basic Concepts and Methods 10  Basic Concepts  Frequent Itemset Mining Methods  Which Patterns Are Interesting?—Pattern Evaluation Methods  Summary
  • 11.
    Scalable Frequent ItemsetMining Methods 11  Apriori: A Candidate Generation-and-Test Approach  Improving the Efficiency of Apriori  FPGrowth: A Frequent Pattern-Growth Approach  ECLAT: Frequent Pattern Mining with Vertical Data Format
  • 12.
    12 The DownwardClosure Property and Scalable Mining Methods  The downward closure property of frequent patterns  Any subset of a frequent itemset must be frequent  If {beer, diaper, nuts} is frequent, so is {beer, diaper}  i.e., every transaction having {beer, diaper, nuts} also contains {beer, diaper}  Scalable mining methods: Three major approaches  Apriori (Agrawal & Srikant@VLDB’94)  Freq. pattern growth (FPgrowth—Han, Pei & Yin @SIGMOD’00)  Vertical data format approach (Charm—Zaki & Hsiao @SDM’02)
  • 13.
    Apriori: A CandidateGeneration & Test Approach 13  Apriori pruning principle: If there is any itemset which is infrequent, its superset should not be generated/tested! (Agrawal & Srikant @VLDB’94, Mannila, et al. @ KDD’ 94)  Method:  Initially, scan DB once to get frequent 1-itemset  Generate length (k+1) candidate itemsets from length k frequent itemsets  Test the candidates against DB  Terminate when no frequent or candidate set can be generated
  • 14.
    14 The AprioriAlgorithm—An Example Database TDB C1 1st scan L1 Tid Items 10 A, C, D 20 B, C, E 30 A, B, C, E 40 B, E L2 Itemset sup {A} 2 {B} 3 {C} 3 {D} 1 {E} 3 C2 C2 2nd scan C3 3rd scan L3 Itemset sup {A} 2 {B} 3 {C} 3 {E} 3 Itemset {A, B} {A, C} {A, E} {B, C} {B, E} {C, E} Itemset sup {A, B} 1 {A, C} 2 {A, E} 1 {B, C} 2 {B, E} 3 {C, E} 2 Itemset sup {A, C} 2 {B, C} 2 {B, E} 3 {C, E} 2 Itemset {B, C, E} Itemset sup {B, C, E} 2 Supmin = 2
  • 15.
    15 The AprioriAlgorithm (Pseudo-Code) Ck: Candidate itemset of size k Lk : frequent itemset of size k L1 = {frequent items}; for (k = 1; Lk !=; k++) do begin Ck+1 = candidates generated from Lk; for each transaction t in database do increment the count of all candidates in Ck+1 that are contained in t Lk+1 = candidates in Ck+1 with min_support end return k Lk;
  • 16.
    16 Implementation ofApriori  How to generate candidates?  Step 1: self-joining Lk  Step 2: pruning  Example of Candidate-generation  L3={abc, abd, acd, ace, bcd}  Self-joining: L3*L3  abcd from abc and abd  acde from acd and ace  Pruning:  acde is removed because ade is not in L3  C4 = {abcd}
  • 17.
    19 Candidate Generation:An SQL Implementation  SQL Implementation of candidate generation  Suppose the items in Lk-1 are listed in an order  Step 1: self-joining Lk-1 insert into Ck select p.item1, p.item2, …, p.itemk-1, q.itemk-1 from Lk-1 p, Lk-1 q where p.item1=q.item1, …, p.itemk-2=q.itemk-2, p.itemk-1 < q.itemk-1  Step 2: pruning forall itemsets c in Ck do forall (k-1)-subsets s of c do if (s is not in Lk-1) then delete c from Ck  Use object-relational extensions like UDFs, BLOBs, and Table functions for efficient implementation [S. Sarawagi, S. Thomas, and R. Agrawal. Integrating association rule mining with relational database systems: Alternatives and implications. SIGMOD’98]
  • 18.
    Scalable Frequent ItemsetMining Methods 20  Apriori: A Candidate Generation-and-Test Approach  Improving the Efficiency of Apriori  FPGrowth: A Frequent Pattern-Growth Approach  ECLAT: Frequent Pattern Mining with Vertical Data Format  Mining Close Frequent Patterns and Maxpatterns
  • 19.
    21 Further Improvementof the Apriori Method  Major computational challenges  Multiple scans of transaction database  Huge number of candidates  Tedious workload of support counting for candidates  Improving Apriori: general ideas  Reduce passes of transaction database scans  Shrink number of candidates  Facilitate support counting of candidates
  • 20.
    Partition: Scan DatabaseOnly Twice  Any itemset that is potentially frequent in DB must be frequent in at least one of the partitions of DB  Scan 1: partition database and find local frequent patterns  Scan 2: consolidate global frequent patterns  A. Savasere, E. Omiecinski and S. Navathe, VLDB’95 DB1 + DB2 + + DBk = DB sup1(i) < σDB1 sup2(i) < σDB2 supk(i) < σDBk sup(i) < σDB
  • 21.
    23 DHP: Reducethe Number of Candidates  A k-itemset whose corresponding hashing bucket count is below the threshold cannot be frequent  Candidates: a, b, c, d, e  Hash entries  {ab, ad, ae}  {bd, be, de}  …  Frequent 1-itemset: a, b, d, e . . .  ab is not a candidate 2-itemset if the sum of count of {ab, ad, ae} is below support threshold  J. Park, M. Chen, and P. Yu. An effective hash-based algorithm for mining association rules. SIGMOD’95 count itemsets 35 {ab, ad, ae} {yz, qs, wt} 88 102 {bd, be, de} . . . Hash Table
  • 22.
    24 Sampling forFrequent Patterns  Select a sample of original database, mine frequent patterns within sample using Apriori  Scan database once to verify frequent itemsets found in sample, only borders of closure of frequent patterns are checked  Example: check abcd instead of ab, ac, …, etc.  Scan database again to find missed frequent patterns  H. Toivonen. Sampling large databases for association rules. In VLDB’96
  • 23.
    25 DIC: ReduceNumber of Scans ABCD ABC ABD ACD BCD AB AC BC AD BD CD A B C D {} Itemset lattice  Once both A and D are determined frequent, the counting of AD begins  Once all length-2 subsets of BCD are determined frequent, the counting of BCD begins Transactions 1-itemsets 2-itemsets … Apriori 1-itemsets 2-items DIC 3-items S. Brin R. Motwani, J. Ullman, and S. Tsur. Dynamic itemset counting and implication rules for market basket data. In SIGMOD’97
  • 24.
    Scalable Frequent ItemsetMining Methods 26  Apriori: A Candidate Generation-and-Test Approach  Improving the Efficiency of Apriori  FPGrowth: A Frequent Pattern-Growth Approach  ECLAT: Frequent Pattern Mining with Vertical Data Format  Mining Close Frequent Patterns and Maxpatterns
  • 25.
    27 Pattern-Growth Approach:Mining Frequent Patterns Without Candidate Generation  Bottlenecks of the Apriori approach  Breadth-first (i.e., level-wise) search  Candidate generation and test  Often generates a huge number of candidates  The FPGrowth Approach (J. Han, J. Pei, and Y. Yin, SIGMOD’ 00)  Depth-first search  Avoid explicit candidate generation  Major philosophy: Grow long patterns from short ones using local frequent items only  “abc” is a frequent pattern  Get all transactions having “abc”, i.e., project DB on abc: DB|abc  “d” is a local frequent item in DB|abc  abcd is a frequent pattern
  • 26.
    28 Construct FP-treefrom a Transaction Database {} f:4 c:1 b:1 p:1 c:3 b:1 a:3 m:2 b:1 p:2 m:1 Header Table Item frequency head f 4 c 4 a 3 b 3 m 3 p 3 min_support = 3 TID Items bought (ordered) frequent items 100 {f, a, c, d, g, i, m, p} {f, c, a, m, p} 200 {a, b, c, f, l, m, o} {f, c, a, b, m} 300 {b, f, h, j, o, w} {f, b} 400 {b, c, k, s, p} {c, b, p} 500 {a, f, c, e, l, p, m, n} {f, c, a, m, p} 1. Scan DB once, find frequent 1-itemset (single item pattern) 2. Sort frequent items in frequency descending order, f-list 3. Scan DB again, construct FP-tree F-list = f-c-a-b-m-p
  • 27.
    29 Partition Patternsand Databases  Frequent patterns can be partitioned into subsets according to f-list  F-list = f-c-a-b-m-p  Patterns containing p  Patterns having m but no p  …  Patterns having c but no a nor b, m, p  Pattern f  Completeness and non-redundency
  • 28.
    30 Find PatternsHaving P From P-conditional Database  Starting at the frequent item header table in the FP-tree  Traverse the FP-tree by following the link of each frequent item p  Accumulate all of transformed prefix paths of item p to form p’s conditional pattern base Conditional pattern bases item cond. pattern base c f:3 a fc:3 b fca:1, f:1, c:1 m fca:2, fcab:1 p fcam:2, cb:1 {} f:4 c:1 b:1 p:1 c:3 b:1 a:3 m:2 b:1 p:2 m:1 Header Table Item frequency head f 4 c 4 a 3 b 3 m 3 p 3
  • 29.
    From Conditional Pattern-basesto Conditional FP-trees All frequent patterns relate to m m, fm, cm, am, fcm, fam, cam, fcam 31  For each pattern-base  Accumulate the count for each item in the base  Construct the FP-tree for the frequent items of the pattern base m-conditional pattern base: fca:2, fcab:1 {} f:3 c:3 a:3   m-conditional FP-tree {} f:4 c:1 b:1 p:1 c:3 b:1 a:3 m:2 b:1 p:2 m:1 Header Table Item frequency head f 4 c 4 a 3 b 3 m 3 p 3
  • 30.
    32 Recursion: MiningEach Conditional FP-tree {} f:3 c:3 a:3 Cond. pattern base of “am”: (fc:3) m-conditional FP-tree {} f:3 c:3 am-conditional FP-tree Cond. pattern base of “cm”: (f:3) {} f:3 cm-conditional FP-tree Cond. pattern base of “cam”: (f:3) {} f:3 cam-conditional FP-tree
  • 31.
    33 A SpecialCase: Single Prefix Path in FP-tree  Suppose a (conditional) FP-tree T has a shared single prefix-path P  Mining can be decomposed into two parts  Reduction of the single prefix path into one node  Concatenation of the mining results of the two parts  {} a1:n1 a2:n2 a3:n3 b1:m1 C1:k1 C2:k2 C3:k3 r1 b1:m1 C1:k1 C2:k2 C3:k3 + {} a1:n1 a2:n2 a3:n3 r1 =
  • 32.
    34 Benefits ofthe FP-tree Structure  Completeness  Preserve complete information for frequent pattern mining  Never break a long pattern of any transaction  Compactness  Reduce irrelevant info—infrequent items are gone  Items in frequency descending order: the more frequently occurring, the more likely to be shared  Never be larger than the original database (not count node-links and the count field)
  • 33.
    35 The FrequentPattern Growth Mining Method  Idea: Frequent pattern growth  Recursively grow frequent patterns by pattern and database partition  Method  For each frequent item, construct its conditional pattern-base, and then its conditional FP-tree  Repeat the process on each newly created conditional FP-tree  Until the resulting FP-tree is empty, or it contains only one path—single path will generate all the combinations of its sub-paths, each of which is a frequent pattern
  • 34.
    36 Scaling FP-growthby Database Projection  What about if FP-tree cannot fit in memory?  DB projection  First partition a database into a set of projected DBs  Then construct and mine FP-tree for each projected DB  Parallel projection vs. partition projection techniques  Parallel projection  Project the DB in parallel for each frequent item  Parallel projection is space costly  All the partitions can be processed in parallel  Partition projection  Partition the DB based on the ordered frequent items  Passing the unprocessed parts to the subsequent partitions
  • 35.
    37 Partition-Based Projection  Parallel projection needs a lot of disk space  Partition projection saves it Tran. DB fcamp fcabm fb cbp fcamp p-proj DB fcam cb fcam m-proj DB fcab fca fca b-proj DB f cb … a-proj DB fc … c-proj DB f … f-proj DB … am-proj DB fc fc fc cm-proj DB f f f …
  • 36.
    38 FP-Growth vs.Apriori: Scalability With the Support Threshold 100 90 80 70 60 50 40 30 20 10 0 Data set T25I20D10K 0 0.5 1 1.5 2 2.5 3 Support threshold(%) Run time(sec.) D1 FP-grow th runtime D1 Apriori runtime
  • 37.
    FP-Growth vs. Tree-Projection:Scalability with the Support Threshold Data Mining: Concepts and Techniques 39 140 120 100 80 60 40 20 0 0 0.5 1 1.5 2 Support threshold (%) Runtime (sec.) D2 FP-growth D2 TreeProjection Data set T25I20D100K
  • 38.
    40 Advantages ofthe Pattern Growth Approach  Divide-and-conquer:  Decompose both the mining task and DB according to the frequent patterns obtained so far  Lead to focused search of smaller databases  Other factors  No candidate generation, no candidate test  Compressed database: FP-tree structure  No repeated scan of entire database  Basic ops: counting local freq items and building sub FP-tree, no pattern search and matching  A good open-source implementation and refinement of FPGrowth  FPGrowth+ (Grahne and J. Zhu, FIMI'03)
  • 39.
    41 Further Improvementsof Mining Methods  AFOPT (Liu, et al. @ KDD’03)  A “push-right” method for mining condensed frequent pattern (CFP) tree  Carpenter (Pan, et al. @ KDD’03)  Mine data sets with small rows but numerous columns  Construct a row-enumeration tree for efficient mining  FPgrowth+ (Grahne and Zhu, FIMI’03)  Efficiently Using Prefix-Trees in Mining Frequent Itemsets, Proc. ICDM'03 Int. Workshop on Frequent Itemset Mining Implementations (FIMI'03), Melbourne, FL, Nov. 2003  TD-Close (Liu, et al, SDM’06)
  • 40.
    Extension of PatternGrowth Mining Methodology 42  Mining closed frequent itemsets and max-patterns  CLOSET (DMKD’00), FPclose, and FPMax (Grahne & Zhu, Fimi’03)  Mining sequential patterns  PrefixSpan (ICDE’01), CloSpan (SDM’03), BIDE (ICDE’04)  Mining graph patterns  gSpan (ICDM’02), CloseGraph (KDD’03)  Constraint-based mining of frequent patterns  Convertible constraints (ICDE’01), gPrune (PAKDD’03)  Computing iceberg data cubes with complex measures  H-tree, H-cubing, and Star-cubing (SIGMOD’01, VLDB’03)  Pattern-growth-based Clustering  MaPle (Pei, et al., ICDM’03)  Pattern-Growth-Based Classification  Mining frequent and discriminative patterns (Cheng, et al, ICDE’07)
  • 41.
    Scalable Frequent ItemsetMining Methods 43  Apriori: A Candidate Generation-and-Test Approach  Improving the Efficiency of Apriori  FPGrowth: A Frequent Pattern-Growth Approach  ECLAT: Frequent Pattern Mining with Vertical Data Format  Mining Close Frequent Patterns and Maxpatterns
  • 42.
    ECLAT: Mining byExploring Vertical Data Format 44  Vertical format: t(AB) = {T11, T25, …}  tid-list: list of trans.-ids containing an itemset  Deriving frequent patterns based on vertical intersections  t(X) = t(Y): X and Y always happen together  t(X)  t(Y): transaction having X always has Y  Using diffset to accelerate mining  Only keep track of differences of tids  t(X) = {T1, T2, T3}, t(XY) = {T1, T3}  Diffset (XY, X) = {T2}  Eclat (Zaki et al. @KDD’97)  Mining Closed patterns using vertical format: CHARM (Zaki & Hsiao@SDM’02)
  • 43.
    Scalable Frequent ItemsetMining Methods 45  Apriori: A Candidate Generation-and-Test Approach  Improving the Efficiency of Apriori  FPGrowth: A Frequent Pattern-Growth Approach  ECLAT: Frequent Pattern Mining with Vertical Data Format  Mining Close Frequent Patterns and Maxpatterns
  • 44.
    Mining Frequent ClosedPatterns: CLOSET  Flist: list of all frequent items in support ascending order  Flist: d-a-f-e-c  Divide search space  Patterns having d  Patterns having d but no a, etc.  Find frequent closed pattern recursively Min_sup=2  Every transaction having d also has cfa  cfad is a frequent closed pattern  J. Pei, J. Han & R. Mao. “CLOSET: An Efficient Algorithm for Mining Frequent Closed Itemsets", DMKD'00. TID Items 10 a, c, d, e, f 20 a, b, e 30 c, e, f 40 a, c, d, f 50 c, e, f
  • 45.
    CLOSET+: Mining ClosedItemsets by Pattern-Growth  Itemset merging: if Y appears in every occurrence of X, then Y is merged with X  Sub-itemset pruning: if Y כ X, and sup(X) = sup(Y), X and all of X’s descendants in the set enumeration tree can be pruned  Hybrid tree projection  Bottom-up physical tree-projection  Top-down pseudo tree-projection  Item skipping: if a local frequent item has the same support in several header tables at different levels, one can prune it from the header table at higher levels  Efficient subset checking
  • 46.
    MaxMiner: Mining Max-Patterns  1st scan: find frequent items  A, B, C, D, E  2nd scan: find support for  AB, AC, AD, AE, ABCDE  BC, BD, BE, BCDE  CD, CE, CDE, DE  Since BCDE is a max-pattern, no need to check BCD, BDE, CDE in later scan  R. Bayardo. Efficiently mining long patterns from databases. SIGMOD’98 Tid Items 10 A, B, C, D, E 20 B, C, D, E, 30 A, C, D, F Potential max-patterns
  • 47.
    CHARM: Mining byExploring Vertical Data Format  Vertical format: t(AB) = {T11, T25, …}  tid-list: list of trans.-ids containing an itemset  Deriving closed patterns based on vertical intersections  t(X) = t(Y): X and Y always happen together  t(X)  t(Y): transaction having X always has Y  Using diffset to accelerate mining  Only keep track of differences of tids  t(X) = {T1, T2, T3}, t(XY) = {T1, T3}  Diffset (XY, X) = {T2}  Eclat/MaxEclat (Zaki et al. @KDD’97), VIPER(P. Shenoy et al.@SIGMOD’00), CHARM (Zaki & Hsiao@SDM’02)
  • 48.
    50 Visualization ofAssociation Rules: Plane Graph
  • 49.
    51 Visualization ofAssociation Rules: Rule Graph
  • 50.
    52 Visualization ofAssociation Rules (SGI/MineSet 3.0)
  • 51.
    53 Computational Complexityof Frequent Itemset Mining  How many itemsets are potentially to be generated in the worst case?  The number of frequent itemsets to be generated is senstive to the minsup threshold  When minsup is low, there exist potentially an exponential number of frequent itemsets  The worst case: MN where M: # distinct items, and N: max length of transactions  The worst case complexty vs. the expected probability  Ex. Suppose Walmart has 104 kinds of products  The chance to pick up one product 10-4  The chance to pick up a particular set of 10 products: ~10-40  What is the chance this particular set of 10 products to be frequent 103 times in 109 transactions?
  • 52.
    Chapter 5: MiningFrequent Patterns, Association and Correlations: Basic Concepts and Methods 54  Basic Concepts  Frequent Itemset Mining Methods  Which Patterns Are Interesting?—Pattern Evaluation Methods  Summary
  • 53.
    55 Interestingness Measure:Correlations (Lift)  play basketball  eat cereal [40%, 66.7%] is misleading  The overall % of students eating cereal is 75% > 66.7%.  play basketball  not eat cereal [20%, 33.3%] is more accurate, although with lower support and confidence  Measure of dependent/correlated events: lift 0.89 P A B ( ) P A P B 2000/ 5000 lif t(B,C)   3000/ 5000*3750/ 5000 Basketball Not basketball Sum (row) Cereal 2000 1750 3750 Not cereal 1000 250 1250 Sum(col.) 3000 2000 5000 ( ) ( ) lift   1.33 1000/ 5000 lif t(B,C)   3000/ 5000*1250/ 5000
  • 54.
    56 Are liftand 2 Good Measures of Correlation?  “Buy walnuts  buy milk [1%, 80%]” is misleading if 85% of customers buy milk  Support and confidence are not good to indicate correlations  Over 20 interestingness measures have been proposed (see Tan, Kumar, Sritastava @KDD’02)  Which are good ones?
  • 55.
  • 56.
    Comparison of InterestingnessMeasures  Null-(transaction) invariance is crucial for correlation analysis  Lift and 2 are not null-invariant  5 null-invariant measures Milk No Milk Sum (row) Coffee m, c ~m, c c No Coffee m, ~c ~m, ~c ~c Sum(col.) m ~m  Kulczynski measure (1927) Null-transactions w.r.t. m and c Null-invariant Subtle: They disagree September 14, 2014 Data Mining: Concepts and Techniques 58
  • 57.
    59 Analysis ofDBLP Coauthor Relationships Recent DB conferences, removing balanced associations, low sup, etc. Advisor-advisee relation: Kulc: high, coherence: low, cosine: middle  Tianyi Wu, Yuguo Chen and Jiawei Han, “Association Mining in Large Databases: A Re-Examination of Its Measures”, Proc. 2007 Int. Conf. Principles and Practice of Knowledge Discovery in Databases (PKDD'07), Sept. 2007
  • 58.
    Which Null-Invariant MeasureIs Better?  IR (Imbalance Ratio): measure the imbalance of two itemsets A and B in rule implications  Kulczynski and Imbalance Ratio (IR) together present a clear picture for all the three datasets D4 through D6  D4 is balanced & neutral  D5 is imbalanced & neutral  D6 is very imbalanced & neutral
  • 59.
    Chapter 5: MiningFrequent Patterns, Association and Correlations: Basic Concepts and Methods 61  Basic Concepts  Frequent Itemset Mining Methods  Which Patterns Are Interesting?—Pattern Evaluation Methods  Summary
  • 60.
    62 Summary Basic concepts: association rules, support-confident framework, closed and max-patterns  Scalable frequent pattern mining methods  Apriori (Candidate generation & test)  Projection-based (FPgrowth, CLOSET+, ...)  Vertical format approach (ECLAT, CHARM, ...)  Which patterns are interesting?  Pattern evaluation methods
  • 61.
    September 14, 2014Data Mining: Concepts and Techniques 63
  • 62.
    64 Ref: BasicConcepts of Frequent Pattern Mining  (Association Rules) R. Agrawal, T. Imielinski, and A. Swami. Mining association rules between sets of items in large databases. SIGMOD'93.  (Max-pattern) R. J. Bayardo. Efficiently mining long patterns from databases. SIGMOD'98.  (Closed-pattern) N. Pasquier, Y. Bastide, R. Taouil, and L. Lakhal. Discovering frequent closed itemsets for association rules. ICDT'99.  (Sequential pattern) R. Agrawal and R. Srikant. Mining sequential patterns. ICDE'95
  • 63.
    65 Ref: Aprioriand Its Improvements  R. Agrawal and R. Srikant. Fast algorithms for mining association rules. VLDB'94.  H. Mannila, H. Toivonen, and A. I. Verkamo. Efficient algorithms for discovering association rules. KDD'94.  A. Savasere, E. Omiecinski, and S. Navathe. An efficient algorithm for mining association rules in large databases. VLDB'95.  J. S. Park, M. S. Chen, and P. S. Yu. An effective hash-based algorithm for mining association rules. SIGMOD'95.  H. Toivonen. Sampling large databases for association rules. VLDB'96.  S. Brin, R. Motwani, J. D. Ullman, and S. Tsur. Dynamic itemset counting and implication rules for market basket analysis. SIGMOD'97.  S. Sarawagi, S. Thomas, and R. Agrawal. Integrating association rule mining with relational database systems: Alternatives and implications. SIGMOD'98.
  • 64.
    66 Ref: Depth-First,Projection-Based FP Mining  R. Agarwal, C. Aggarwal, and V. V. V. Prasad. A tree projection algorithm for generation of frequent itemsets. J. Parallel and Distributed Computing:02.  J. Han, J. Pei, and Y. Yin. Mining frequent patterns without candidate generation. SIGMOD’ 00.  J. Liu, Y. Pan, K. Wang, and J. Han. Mining Frequent Item Sets by Opportunistic Projection. KDD'02.  J. Han, J. Wang, Y. Lu, and P. Tzvetkov. Mining Top-K Frequent Closed Patterns without Minimum Support. ICDM'02.  J. Wang, J. Han, and J. Pei. CLOSET+: Searching for the Best Strategies for Mining Frequent Closed Itemsets. KDD'03.  G. Liu, H. Lu, W. Lou, J. X. Yu. On Computing, Storing and Querying Frequent Patterns. KDD'03.  G. Grahne and J. Zhu, Efficiently Using Prefix-Trees in Mining Frequent Itemsets, Proc. ICDM'03 Int. Workshop on Frequent Itemset Mining Implementations (FIMI'03), Melbourne, FL, Nov. 2003
  • 65.
    67 Ref: VerticalFormat and Row Enumeration Methods  M. J. Zaki, S. Parthasarathy, M. Ogihara, and W. Li. Parallel algorithm for discovery of association rules. DAMI:97.  Zaki and Hsiao. CHARM: An Efficient Algorithm for Closed Itemset Mining, SDM'02.  C. Bucila, J. Gehrke, D. Kifer, and W. White. DualMiner: A Dual- Pruning Algorithm for Itemsets with Constraints. KDD’02.  F. Pan, G. Cong, A. K. H. Tung, J. Yang, and M. Zaki , CARPENTER: Finding Closed Patterns in Long Biological Datasets. KDD'03.  H. Liu, J. Han, D. Xin, and Z. Shao, Mining Interesting Patterns from Very High Dimensional Data: A Top-Down Row Enumeration Approach, SDM'06.
  • 66.
    68 Ref: MiningCorrelations and Interesting Rules  M. Klemettinen, H. Mannila, P. Ronkainen, H. Toivonen, and A. I. Verkamo. Finding interesting rules from large sets of discovered association rules. CIKM'94.  S. Brin, R. Motwani, and C. Silverstein. Beyond market basket: Generalizing association rules to correlations. SIGMOD'97.  C. Silverstein, S. Brin, R. Motwani, and J. Ullman. Scalable techniques for mining causal structures. VLDB'98.  P.-N. Tan, V. Kumar, and J. Srivastava. Selecting the Right Interestingness Measure for Association Patterns. KDD'02.  E. Omiecinski. Alternative Interest Measures for Mining Associations. TKDE’03.  T. Wu, Y. Chen and J. Han, “Association Mining in Large Databases: A Re-Examination of Its Measures”, PKDD'07
  • 67.
    69 Ref: Freq.Pattern Mining Applications  Y. Huhtala, J. Kärkkäinen, P. Porkka, H. Toivonen. Efficient Discovery of Functional and Approximate Dependencies Using Partitions. ICDE’98.  H. V. Jagadish, J. Madar, and R. Ng. Semantic Compression and Pattern Extraction with Fascicles. VLDB'99.  T. Dasu, T. Johnson, S. Muthukrishnan, and V. Shkapenyuk. Mining Database Structure; or How to Build a Data Quality Browser. SIGMOD'02.  K. Wang, S. Zhou, J. Han. Profit Mining: From Patterns to Actions. EDBT’02.