Suppose we would like to extract positive and negative itemsets from a data set that contains d items.
(a) Consider an approach where we introduce a new variable to represent
each negative item. With this approach, the number of items grows
from d to 2d. What is the total size of the itemset lattice, assuming
that an itemset may contain both positive and negative items of the
same variable?
(b) Assume that an itemset must contain positive or negative items of dif-
ferent variables. For example, the itemset {a, a, b, c} is invalid because
it contains both positive and negative items for variable a. What is the
total size of the itemset lattice?
(a)
(b)
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