This question appears in Mumbai University > Human Machine Interaction subject

Terms:-

i. Item set

ii. Frequent item set

iii. Closed item set

i.Item set: Def: A
collection
of
one
or
more
items.

• Example:
{Milk,
Bread,
Diaper}


k item set : An
 item set 
that contains 
k
 items

ii.Frequent item set:

Def: An
itemset
whose
support
is
greater
than
or
equal
to
a
minimum support threshold.


iii.Closed item set:

Def: It is a frequent item set that is both closed and its support is greater than or equal to minimum support.

An item set is closed in a data set if there exists no super set that has the same support count as this original itemset.

Eg:

• The diagram shows the, frequent and closed item sets.
• The item sets that are underlined are the frequent item sets.
• In order to determine which of the frequent item sets are closed, all you have to do is check to see if they have the same support as their super sets, if they do they are not closed.
• For example ad is a frequent item set but has the same support as abd so it is NOT a closed frequent item set; c on the other hand is a closed frequent item set because all of its super sets, ac, bc, and cd have supports that are less than 3.