tokens_group {quanteda}

Combine documents in a tokens object by a grouping variable

Description

Combine documents in a tokens object by a grouping variable, by concatenating the tokens in the order of the documents within each grouping variable.

Usage

tokens_group(x, groups = docid(x), fill = FALSE, env = NULL)

Arguments

x

tokens object

groups

grouping variable for sampling, equal in length to the number of documents. This will be evaluated in the docvars data.frame, so that docvars may be referred to by name without quoting. This also changes previous behaviours for groups. See news(Version >= "3.0", package = "quanteda") for details.

fill

logical; if TRUE and groups is a factor, then use all levels of the factor when forming the new documents of the grouped object. This will result in a new "document" with empty content for levels not observed, but for which an empty document may be needed. If groups is a factor of dates, for instance, then fill = TRUE ensures that the new object will consist of one new "document" by date, regardless of whether any documents previously existed with that date. Has no effect if the groups variable(s) are not factors.

env

an environment or a list object in which x is searched. Passed to substitute for non-standard evaluation.

Value

a tokens object whose documents are equal to the unique group combinations, and whose tokens are the concatenations of the tokens by group. Document-level variables that have no variation within groups are saved in docvars. Document-level variables that are lists are dropped from grouping, even when these exhibit no variation within groups.

Examples

corp <- corpus(c("a a b", "a b c c", "a c d d", "a c c d"),
               docvars = data.frame(grp = c("grp1", "grp1", "grp2", "grp2")))
toks <- tokens(corp)
tokens_group(toks, groups = grp)
tokens_group(toks, groups = c(1, 1, 2, 2))

# with fill
tokens_group(toks, groups = factor(c(1, 1, 2, 2), levels = 1:3))
tokens_group(toks, groups = factor(c(1, 1, 2, 2), levels = 1:3), fill = TRUE)