subset: Subsetting Itemsets, Rules and Transactions

Description

Provides the generic function subset() and methods to subset associations or transactions (itemMatrix) which meet certain conditions (e.g., contains certain items or satisfies a minimum lift).

Usage

subset(x, ...)
# S4 method for itemMatrix
subset(x, subset, ...)
# S4 method for itemsets
subset(x, subset, ...)
# S4 method for rules
subset(x, subset, ...)

Value

An object of the same class as x containing only the elements which satisfy the conditions.

Arguments

x: object to be subsetted.
...: further arguments to be passed to or from other methods.
subset: logical expression indicating elements to keep.

Author

Michael Hahsler

Details

subset() finds the rows/itemsets/rules of x that match the expression given in subset. Parts of x like items, lhs, rhs and the columns in the quality data.frame (e.g., support and lift) can be directly referred to by their names in subset.

Important operators to select itemsets containing items specified by their labels are

%in%: select itemsets matching any given item
%ain%: select only itemsets matching all given item
%oin%: select only itemsets matching only the given item
%pin%: %in% with partial matching

Examples

Run this code

data("Adult")
rules <- apriori(Adult)

## select all rules with item "marital-status=Never-married" in
## the right-hand-side and lift > 2
rules.sub <- subset(rules, subset = rhs %in% "marital-status=Never-married" &
  lift > 2)

## use partial matching for all items corresponding to the variable
## "marital-status"
rules.sub <- subset(rules, subset = rhs %pin% "marital-status=")

## select only rules with items "age=Young" and "workclass=Private" in
## the left-hand-side
rules.sub <- subset(rules, subset = lhs %ain%
  c("age=Young", "workclass=Private"))

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