R: Read Transaction Data

read.transactions {arules}

R Documentation

Read Transaction Data

Description

Reads a transaction data file from disk and creates a transactions object.

Usage

read.transactions(file, format = c("basket", "single"), 
                  header = FALSE, sep = "", 
                  cols = NULL, rm.duplicates = FALSE, 
                  quote = "\"'", skip = 0, 
                  encoding = "unknown")

Arguments

`file`	the file name or connection.
`format`	a character string indicating the format of the data set. One of `"basket"` or `"single"`, can be abbreviated.
`header`	a logical value indicating whether the file contains the names of the variables as its first line.
`sep`	a character string specifying how fields are separated in the data file. The default (`""`) splits at whitespaces.
`cols`	For the ‘single’ format, `cols` is a numeric or character vector of length two giving the numbers or names of the columns (fields) with the transaction and item ids, respectively. If character, the first line of `file` is assumed to be a header with column names. For the ‘basket’ format, `cols` can be a numeric scalar giving the number of the column (field) with the transaction ids. If `cols = NULL`, the data do not contain transaction ids.
`rm.duplicates`	a logical value specifying if duplicate items should be removed from the transactions.
`quote`	a list of characters used as quotes when reading.
`skip`	number of lines to skip in the file before start reading data.
`encoding`	character string indicating the encoding which is passed to `readLines` or `scan` (see `Encoding`).

Details

For ‘basket’ format, each line in the transaction data file represents a transaction where the items (item labels) are separated by the characters specified by sep. For ‘single’ format, each line corresponds to a single item, containing at least ids for the transaction and the item.

Value

Returns an object of class transactions.

Author(s)

Michael Hahsler and Kurt Hornik

Examples

## create a demo file using basket format for the example
data <- paste(
  "# this is some test data", 
  "item1, item2", 
  "item1", 
  "item2, item3", 
  sep="\n")
cat(data)
write(data, file = "demo_basket.txt")

## read demo data (skip the comment in the first line)
tr <- read.transactions("demo_basket.txt", format = "basket", sep=",", skip = 1)
inspect(tr)
## make always sure that the items were properly separated
itemLabels(tr)

## create a demo file using single format for the example
## column 1 contains the transaction ID and column 2 contains one item
data <- paste(
  "trans1 item1", 
  "trans2 item1",
  "trans2 item2", 
  sep ="\n")
cat(data)
write(data, file = "demo_single.txt")

## read demo data
tr <- read.transactions("demo_single.txt", format = "single", cols = c(1,2))
inspect(tr)

## create a demo file using single format with column headers
data <- paste(
  "item_id;trans_id",
  "item1;trans1", 
  "item1;trans2",
  "item2;trans2", 
  sep ="\n")
cat(data)
write(data, file = "demo_single.txt")

## read demo data
tr <- read.transactions("demo_single.txt", format = "single", 
  header = TRUE, sep = ";", cols = c("trans_id","item_id"))
inspect(tr)

## tidy up
unlink("demo_basket.txt")
unlink("demo_single.txt")

[Package arules version 1.7-2 Index]