A Database has four transactions. Let minimum support and confidence be 50%.

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A Database has four transactions. Let minimum support and confidence be 50%.

Tid	Items bought
1	A,B,D
2	A,D
3	A,C
4	B,D,E,F

 Find out the frequent item sets and strong association rules for the above example using Apriori Algorithm.

Ans.

Step 1: Scan for support count of each candidate –{A,B,C,D,E,F}

C1=

Item	Support
A	¾ =75%
B	2/4=50%
C	¼=25%
D	¾=75%
E	¼=25%
F	¼=25%

Step 2: Comparing with the min support threshold count of 50%.

 L1=

Item	Support
A	3
B	2
D	3

Step 3: Generate candidate C2 from L1.

C2:

Item

{A,B}

{A,D}

{B,D}

Step 4:

Scan for support count of each candidate in C2.

Item	Support
{A,B}	¼=25%
{A,D}	2/4=50%
{B,D}	¼=25%

Step 5:

Compare C2 with minimum support

L2=

Items	Support
{A,D}	2

Step 6: Data contains frequent item {A,D}

Therefore the association rule that can be generated from L are:

Association Rule	Support	Confidence
A->D	2	2/3 = 66%
D->A	2	2/2=100%

As minimum confidence threshold is 50%, then both the rules are output as showing the confidence above 50%.

The rules are:

Rule 1: A->D

Rule 2: D->A