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`:
  always an empty data.frame for transaction ID lists.
`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 = "dgCMatrix")`
coerce
  `signature(from = "tidLists", to = "list")`
coerce
  `signature(from = "tidLists", to = "matrix")`
coerce
  `signature(from = "tidLists", to = "itemMatrix")`
coerce
  `signature(from = "tidLists", to = "transactions")`
coerce
  `signature(from = "itemMatrix", to = "tidLists")`
coerce
  `signature(from = "transactions", to = "tidLists")`
dim
  `signature(x = "tidLists")`; returns the dimensions of the sparse Matrix representing the `tidLists`.
itemInfo
  returns the slot `itemInfo`.
itemLabels
  `signature(object = "tidLists")`; returns the item labels as a character vector.
labels
  `signature(x = "transactions")`; returns the labels (item labels and transaction IDs) for the incidence matrix as a list of two vectors named `items` and `transactionID`.
show
  `signature(object = "tidLists")`
summary
  `signature(object = "tidLists")`
transactionInfo
  `signature(x = "transactions")`: returns the slot `transactionInfo`.

### 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")
      )
    t <- as(data, "transactions")

    ## Mine itemsets with tidLists.
    f <- eclat(data, parameter = list(support = 0, tidLists = TRUE))

    ## Get dimensions of the tidLists.
    dim(tidLists(f))

    ## Coerce tidLists to list.
    as(tidLists(f), "list")

    ## Inspect visually.
    image(tidLists(f))

[Package arules version 0.6-3 Index]