Take a random sample of documents of the specified size from a corpus, with or without replacement, optionally by grouping variables or with probability weights.

tokens_sample(x, size = NULL, replace = FALSE, prob = NULL, by = NULL)

Arguments

x

a tokens object whose documents will be sampled

size

a positive number, the number of documents to select; when used with by, the number to select from each group or a vector equal in length to the number of groups defining the samples to be chosen in each category of by. By defining a size larger than the number of documents, it is possible to oversample when replace = TRUE.

replace

if TRUE, sample with replacement

prob

a vector of probability weights for obtaining the elements of the vector being sampled. May not be applied when by is used.

by

optional grouping variable for sampling. 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 by. See news(Version >= "2.9", package = "quanteda") for details.

Value

a tokens object (re)sampled on the documents, containing the document variables for the documents sampled.

See also

Examples

set.seed(123) toks <- tokens(data_corpus_inaugural[1:6]) toks
#> Tokens consisting of 6 documents and 4 docvars. #> 1789-Washington : #> [1] "Fellow-Citizens" "of" "the" "Senate" #> [5] "and" "of" "the" "House" #> [9] "of" "Representatives" ":" "Among" #> [ ... and 1,525 more ] #> #> 1793-Washington : #> [1] "Fellow" "citizens" "," "I" "am" "again" #> [7] "called" "upon" "by" "the" "voice" "of" #> [ ... and 135 more ] #> #> 1797-Adams : #> [1] "When" "it" "was" "first" "perceived" "," #> [7] "in" "early" "times" "," "that" "no" #> [ ... and 2,565 more ] #> #> 1801-Jefferson : #> [1] "Friends" "and" "Fellow" "Citizens" ":" "Called" #> [7] "upon" "to" "undertake" "the" "duties" "of" #> [ ... and 1,911 more ] #> #> 1805-Jefferson : #> [1] "Proceeding" "," "fellow" "citizens" #> [5] "," "to" "that" "qualification" #> [9] "which" "the" "Constitution" "requires" #> [ ... and 2,368 more ] #> #> 1809-Madison : #> [1] "Unwilling" "to" "depart" "from" "examples" "of" #> [7] "the" "most" "revered" "authority" "," "I" #> [ ... and 1,249 more ] #>
tokens_sample(toks)
#> Tokens consisting of 6 documents and 4 docvars. #> 1797-Adams : #> [1] "When" "it" "was" "first" "perceived" "," #> [7] "in" "early" "times" "," "that" "no" #> [ ... and 2,565 more ] #> #> 1809-Madison : #> [1] "Unwilling" "to" "depart" "from" "examples" "of" #> [7] "the" "most" "revered" "authority" "," "I" #> [ ... and 1,249 more ] #> #> 1793-Washington : #> [1] "Fellow" "citizens" "," "I" "am" "again" #> [7] "called" "upon" "by" "the" "voice" "of" #> [ ... and 135 more ] #> #> 1801-Jefferson : #> [1] "Friends" "and" "Fellow" "Citizens" ":" "Called" #> [7] "upon" "to" "undertake" "the" "duties" "of" #> [ ... and 1,911 more ] #> #> 1805-Jefferson : #> [1] "Proceeding" "," "fellow" "citizens" #> [5] "," "to" "that" "qualification" #> [9] "which" "the" "Constitution" "requires" #> [ ... and 2,368 more ] #> #> 1789-Washington : #> [1] "Fellow-Citizens" "of" "the" "Senate" #> [5] "and" "of" "the" "House" #> [9] "of" "Representatives" ":" "Among" #> [ ... and 1,525 more ] #>
tokens_sample(toks, replace = TRUE) %>% docnames()
#> [1] "1805-Jefferson.1" "1801-Jefferson.1" "1809-Madison.1" #> [4] "1809-Madison.2" "1789-Washington.1" "1793-Washington.1"
tokens_sample(toks, size = 3, replace = TRUE) %>% docnames()
#> [1] "1797-Adams.1" "1805-Jefferson.1" "1797-Adams.2"
# sampling using by docvars(toks)
#> Year President FirstName Party #> 1 1789 Washington George none #> 2 1793 Washington George none #> 3 1797 Adams John Federalist #> 4 1801 Jefferson Thomas Democratic-Republican #> 5 1805 Jefferson Thomas Democratic-Republican #> 6 1809 Madison James Democratic-Republican
tokens_sample(toks, size = 2, replace = TRUE, by = Party) %>% docnames()
#> [1] "1809-Madison.1" "1801-Jefferson.1" "1797-Adams.1" #> [4] "1797-Adams.2" "1789-Washington.1" "1789-Washington.2"