tidLists-class {arules} | R Documentation

## Class tidLists — Transaction ID Lists for Items/Itemsets

### Description

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 from the Class

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", ...)`.

### Slots

`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.

### Methods

coerce

  `signature(from = "tidLists", to = "ngCMatrix")`; access the sparse matrix representation. In the `ngCMatrix` each column represents the transaction IDs for one item/itemset.

coerce

  `signature(from = "tidLists", to = "list")`

coerce

  `signature(from = "list", to = "tidLists")`

coerce

  `signature(from = "tidLists", to = "matrix")`

coerce

  `signature(from = "tidLists", to = "itemMatrix")`

coerce

  `signature(from = "tidLists", to = "transactions")`

coerce

  `signature(from = "itemMatrix", to = "tidLists")`; this also coerces from `transactions`.

coerce

  `signature(from = "transactions", to = "tidLists")`

c

  `signature(x = "tidLists")`; combine.

dim

  `signature(x = "tidLists")`; returns the dimensions of the sparse Matrix representing the `tidLists`.

dimnames, rownames, colnames

  `signature(x = "transactions")`; returns row (items/itemsets) and column (transactionIDs if available) names.

labels

  `signature(x = "transactions")`; returns the labels for the itemsets in each transaction (see `itemMatrix`).

inspect

  inspect the transaction ID lists.

itemInfo

  returns the slot `itemInfo`.

itemLabels

  `signature(object = "tidLists")`; returns the item labels as a character vector.

labels

  `signature(x = "transactions")`; returns the labels (transaction IDs).

show

  `signature(object = "tidLists")`

summary

  `signature(object = "tidLists")`

transactionInfo

  `signature(x = "transactions")`: returns the slot `transactionInfo`.

### Author(s)

Michael Hahsler

### See Also

`[-methods`, `LIST`, `eclat`, `image`, `length`, `size`, `ngCMatrix`(in Matrix), `itemMatrix-class`, `itemsets-class`, `transactions-class`

### Examples

    ## 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)

[Package arules version 1.6-3 Index]