Class tidLists — Transaction ID Lists for Items/Itemsets
Transaction ID lists contains a set of lists. Each list is associated with
an item/itemset and stores the IDs of the transactions which support the
item/itemset. tidLists
uses the class
ngCMatrix
to efficiently store the
transaction ID lists as a sparse matrix. Each column in the matrix
represents one transaction ID list.
tidLists
can be used for different purposes. For some operations
(e.g., support counting) it is efficient to coerce a
transactions
database into tidLists
where each
list contains the transaction IDs for an item (and the support is given by
the length of the list).
The implementation of the Eclat mining algorithm (which uses transaction ID
list intersection) can also produce transaction ID lists for the found
itemsets as part of the returned itemsets
object. These
lists can then be used for further computation.
Objects are created by Eclat if the eclat
function is called
with tidLists = TRUE
in the ECparameter
object,
and returned as part of the mined itemsets
. Objects can
also be created by coercion from an object of class
transactions
or by calls of the form
new("tidLists", ...)
.
data
:object of class
ngCMatrix
.
itemInfo
:a data.frame to store item/itemset labels (see
itemMatrix
class).
transactionInfo
:a data.frame with vectors of the same length as the number of transactions. Each vector can hold additional information e.g., store transaction IDs or user IDs for each transaction.
signature(from = "tidLists", to = "ngCMatrix")
;
access the sparse matrix representation. In the
ngCMatrix
each column represents the transaction IDs
for one item/itemset.
signature(from = "tidLists", to = "list")
signature(from = "list", to = "tidLists")
signature(from = "tidLists", to = "matrix")
signature(from = "tidLists", to = "itemMatrix")
signature(from = "tidLists", to = "transactions")
signature(from = "itemMatrix", to = "tidLists")
; this also coerces from transactions
.
signature(from = "transactions", to = "tidLists")
signature(x = "tidLists")
; combine.
signature(x = "tidLists")
;
returns the dimensions of the sparse Matrix representing the
tidLists
.
signature(x = "transactions")
;
returns row (items/itemsets) and column
(transactionIDs if available) names.
signature(x = "transactions")
;
returns the labels for the itemsets in each transaction
(see itemMatrix
).
inspect the transaction ID lists.
returns the slot itemInfo
.
signature(object = "tidLists")
;
returns the item labels as a character vector.
signature(x = "transactions")
;
returns the labels (transaction IDs).
signature(object = "tidLists")
signature(object = "tidLists")
signature(x = "transactions")
:
returns the slot transactionInfo
.
Michael Hahsler
[-methods
,
LIST
,
eclat
,
image
,
length
,
size
,
ngCMatrix
(in Matrix),
itemMatrix-class
,
itemsets-class
,
transactions-class
## Create transaction data set. data <- list( c("a","b","c"), c("a","b"), c("a","b","d"), c("b","e"), c("b","c","e"), c("a","d","e"), c("a","c"), c("a","b","d"), c("c","e"), c("a","b","d","e") ) data <- as(data, "transactions") data ## convert transactions to transaction ID lists tl <- as(data, "tidLists") tl inspect(tl) dim(tl) dimnames(tl) ## inspect visually image(tl) ## mine itemsets with transaction ID lists f <- eclat(data, parameter = list(support = 0, tidLists = TRUE)) tl2 <- tidLists(f) inspect(tl2)
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