itemMatrix-class {arules} | R Documentation |
The itemMatrix
class is the basic building block
for transactions, itemsets and rules in package arules.
The class contains a sparse Matrix representation of items (a set of
itemsets or transactions) and the corresponding item labels.
Objects can be created by calls of the form new("itemMatrix",
...)
.
However, most of the time objects will be created by coercion from a
matrix
, list
or data.frame
.
data
:dgCMatrix
which stores
item occurrences in sparse representation. Note that the
dgCMatrix
is column-oriented and itemMatrix
is
row-oriented with each row representing an element (an itemset, a
transaction, etc.). As a result, the dgCMatrix
in this
slot is always a transposed version of the binary incidence matrix
in itemMatrix
.
itemInfo
:"data.frame"
which
contains named vectors of the length equal to the number of
elements in the set. If the slot is not empty (contains no item
labels), the first element in the data.frame
must have the
name "labels"
and contain a character vector with the item
labels used for representing an item. In addition to the item
labels, the data.frame
can contain arbitrary named vectors
(of the same length) to represent, e.g., variable names and values
which were used to create the binary items or hierarchical
category information associated with each item label. This
information is used for the %in%
method in this
class. The subset method in associations can use this method to
select subsets of associations containing items with matching
variable or category names.
signature(x = "itemMatrix")
;
extracts parts of the itemMatrix
. The first argument
selects rows (e.g., transactions or rules) and the second argument
selects columns (items).
Either argument can be omitted to select all rows or columns.signature(from = "matrix", to = "itemMatrix")
signature(from = "list", to = "itemMatrix")
signature(from = "itemMatrix", to = "matrix")
signature(from = "itemMatrix", to = "list")
signature(x = "itemMatrix")
;
decodes the numeric items codes (column numbers in the itemMatrix)
given in argument items
to the item names using the labels
stored in x
.
items
can be a vector or list.signature(x = "itemMatrix")
;
returns the dimensions of the itemMatrix.signature(x = "itemMatrix")
;
plots an image of the itemMatrix for visual inspection.signature(x = "itemMatrix")
: matches values
against the item labels (and the additional information) for
each element (row) in the itemMatrix.signature(object = "itemMatrix")
;
returns the item labels as a character
vector.signature(object = "itemMatrix")
;
replaces the item labels.signature(object = "itemMatrix")
;
returns the whole item information data.frame
including
labels.signature(object = "itemMatrix")
;
replaces the item info by a data.frame
.
The length of the vectors in the data.frame
has to match
the number of elements (rows) in the itemMatrix.signature(x = "itemMatrix")
;
returns the number of elements (rows) in the itemMatrix.signature(object = "itemMatrix")
signature(object = "itemMatrix")
Michael Hahsler
transactions-class
,
itemsets-class
,
rules-class
## Generate random data and coerce data to itemMatrix. m <- matrix(as.integer(runif(100000)>0.8), ncol=20) dimnames(m) <- list(NULL, paste("item", c(1:20), sep="")) i <- as(m, "itemMatrix") ## Get the number of elements (rows) in the itemMatrix. length(i) ## Get first 5 elements (rows) of the itemMatrix as list. as(i[1:5], "list")