Iteminfoitemmatrix method returns the whole

• itemInfo,itemMatrix-method : returns the whole item/column information data.frame in-
cluding labels.
• itemInfo<-,itemMatrix-method : replaces the item/column info by a data.frame.
• itemsetInfo,itemMatrix-method : returns the item set/row information data.frame.
• itemsetInfo<-,itemMatrix-method : replaces the item set/row info by a data.frame.
• dimnames,itemMatrix-method : returns a list with the dimname vectors.
• dimnames<-,itemMatrix,list-method : replace the dimnames.

74 itemMatrix-class
Slots
data a sparse matrix of class ngCMatrix representing the itemsets. Note: the matrix is stored for
efficiency reasons transposed! .
itemInfo a data.frame
itemsetInfo a data.frame
Objects from the Class
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.
Coercion
• as("matrix", "itemMatrix")
• as("itemMatrix", "matrix")
• as("list", "itemMatrix")
• as("itemMatrix", "list")
• as("itemMatrix", "ngCMatrix")
• as("ngCMatrix", "itemMatrix")
Author(s)
Michael Hahsler
See Also
Other itemMatrix and transactions functions: abbreviate () , crossTable () , c () , duplicated () ,
extract , hierarchy , image () , inspect () , is.superset () , itemFrequencyPlot () , itemFrequency () ,
match () , merge () , random.transactions () , sample () , sets , size () , supportingTransactions () ,
tidLists-class , transactions-class , unique ()
Examples
set.seed(1234)
## Generate a logical matrix with 5000 random itemsets for 20 items
m <- matrix(runif(5000 * 20) > 0.8, ncol = 20,
dimnames = list(NULL, paste("item", c(1:20), sep = "")))
head(m)
## Coerce the logical matrix into an itemMatrix object
imatrix <- as(m, "itemMatrix")
imatrix
## An itemMatrix contains a set of itemsets (each row is an itemset).
## The length of the set is the number of rows.
length(imatrix)

itemMatrix-class 75
## The sparese matrix also has regular matrix dimensions.
dim(imatrix)
nrow(imatrix)
ncol(imatrix)
## Subsetting: Get first 5 elements (rows) of the itemMatrix. This can be done in
## several ways.
imatrix[1:5] ### get elements 1:5
imatrix[1:5, ] ### Matrix subsetting for rows 1:5
head(imatrix, n = 5) ### head()
## Get first 5 elements (rows) of the itemMatrix as list.
as(imatrix[1:5], "list")
## Get first 5 elements (rows) of the itemMatrix as matrix.
as(imatrix[1:5], "matrix")
## Get first 5 elements (rows) of the itemMatrix as sparse ngCMatrix.
## Warning: For efficiency reasons, the ngCMatrix is transposed!
as(imatrix[1:5], "ngCMatrix")
## Get labels for the first 5 itemsets (first default and then with
## custom formating)
labels(imatrix[1:5])
labels(imatrix[1:5], itemSep = " + ", setStart = "", setEnd = "")
## Create itemsets manually from an itemMatrix. Itemsets contain items in the form of
## an itemMatrix and additional quality measures (not supplied in the example).
is <- new("itemsets", items = imatrix)
is
inspect(head(is, n = 3))
## Create rules manually. I use imatrix[4:6] for the lhs of the rules and
## imatrix[1:3] for the rhs. Rhs and lhs cannot share items so I use
## itemSetdiff here. I also assign missing values for the quality measures support
## and confidence.