# itemFrequency-methods

##### Count Items or Itemsets

`itemFrequency`

counts the number of distinct occurrences of items
or itemsets (elements) in a collection of sequences. That is, multiple
occurrences within a sequence are ignored.

`itemTable`

cross-tabulates the counts an item or itemset
occurs in a sequence.

`nitems`

computes the total number of distinct occurrences of items
or itemsets in a collection of sequences.

`dim`

retrieves the dimensions of an object of class
`'>sequences`

or `'>timedsequences`

.

`length`

retrieves the number of elements of a collection of
sequences or sequence rules.

- Keywords
- models

##### Usage

```
# S4 method for sequences
itemFrequency(x, itemsets = FALSE, type = c("absolute", "relative"))
```# S4 method for sequences
itemTable(x, itemsets = FALSE)

# S4 method for sequences
nitems(x, itemsets = FALSE)

# S4 method for sequences
dim(x)

# S4 method for timedsequences
dim(x)

# S4 method for sequences
length(x)

# S4 method for sequencerules
length(x)

##### Arguments

- x
an object.

- itemsets
a logical value specifying the type of count.

- type
a string value specifying the scale of count.

##### Value

For `itemFrequency`

returns a vector of counts corresponding with
the reference set of distinct items or itemsets.

For `itemTable`

returns a table with the rownames corresponding
with the reference set of distinct items or itemsets.

For `nitems`

a scalar value.

For `dim`

and class `sequences`

a vector of length three
containing the number of sequences and the dimension of the reference
set of distinct itemsets. For class `timedsequences`

the fourth
element contains the number of distinct event times.

For `length`

a scalar value.

##### Note

For efficiency reasons, the reference set of distinct itemsets can be larger than the set actually referenced by a collection of sequences. Thus, the counts of some items or itemsets may be zero.

Method `nitems`

is provided for efficiency; method `dim`

for
technical information.

For analysis of a set of rules use the accessors `lhs`

or `rhs`

, or coerce to sequences.

##### See Also

##### Examples

```
# NOT RUN {
## continue example
example(cspade)
##
itemFrequency(s2)
itemFrequency(s2, itemsets = TRUE)
##
itemTable(s2)
itemTable(s2, itemsets = TRUE)
##
nitems(s2)
nitems(s2, itemsets = TRUE)
##
length(s2)
dim(s2)
##
z <- as(zaki, "timedsequences")
dim(z)
# }
```

*Documentation reproduced from package arulesSequences, version 0.2-19, License: GPL-2*