polmineR: subset – R documentation

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subset

Subsetting corpora and subcorpora

Description

The structural attributes of a corpus (s-attributes) can be used to generate subcorpora (i.e. a subcorpus class object) by applying the subset-method. To obtain a subcorpus, the subset-method can be applied on a corpus represented by a corpus object, a length-one character vector (as a shortcut), and on a subcorpus object.

Usage

## S4 method for signature 'corpus'
subset(x, subset, regex = FALSE, ...)

## S4 method for signature 'character'
subset(x, ...)

## S4 method for signature 'subcorpus'
subset(x, subset, ...)

## S4 method for signature 'remote_corpus'
subset(x, subset)

Arguments

`x`	A `corpus` or `subcorpus` object. A corpus may also specified by a length-one `character` vector.
`subset`	A `logical` expression indicating elements or rows to keep. The expression may be unevaluated (using `quote` or `bquote`).
`regex`	A `logical` value. If `TRUE`, values for s-attributes defined using the three dots (...) are interpreted as regular expressions and passed into a `grep` call for subsetting a table with the regions and values of structural attributes. If `FALSE` (the default), values for s-attributes must match exactly.
`...`	An expression that will be used to create a subcorpus from s-attributes.

Examples

use("polmineR")

# examples for standard and non-standard evaluation
a <- corpus("GERMAPARLMINI")

# subsetting a corpus object using non-standard evaluation 
sc <- subset(a, speaker == "Angela Dorothea Merkel")
sc <- subset(a, speaker == "Angela Dorothea Merkel" & date == "2009-10-28")
sc <- subset(a, grepl("Merkel", speaker))
sc <- subset(a, grepl("Merkel", speaker) & date == "2009-10-28")

# subsetting corpus specified by character vector 
sc <- subset("GERMAPARLMINI", grepl("Merkel", speaker))
sc <- subset("GERMAPARLMINI", speaker == "Angela Dorothea Merkel")
sc <- subset("GERMAPARLMINI", speaker == "Angela Dorothea Merkel" & date == "2009-10-28")
sc <- subset("GERMAPARLMINI", grepl("Merkel", speaker) & date == "2009-10-28")

# subsetting a corpus using the (old) logic of the partition-method
sc <- subset(a, speaker = "Angela Dorothea Merkel")
sc <- subset(a, speaker = "Angela Dorothea Merkel", date = "2009-10-28")
sc <- subset(a, speaker = "Merkel", regex = TRUE)
sc <- subset(a, speaker = c("Merkel", "Kauder"), regex = TRUE)
sc <- subset(a, speaker = "Merkel", date = "2009-10-28", regex = TRUE)

# providing the value for s-attribute as a variable
who <- "Volker Kauder"
sc <- subset(a, quote(speaker == who))

# use bquote for quasiquotation when using a variable for subsetting in a loop
for (who in c("Angela Dorothea Merkel", "Volker Kauder", "Ronald Pofalla")){
   sc <- subset(a, bquote(speaker == .(who)))
   if (interactive()) print(size(sc))
}

# equivalent procedure with lapply (DOES NOT WORK YET)
b <- lapply(
  c("Angela Dorothea Merkel", "Volker Kauder", "Ronald Pofalla"),
  function(who) subset(a, bquote(speaker == .(who)))
)
sapply(b, size)

polmineR

Verbs and Nouns for Corpus Analysis

v0.8.5

GPL-3

Authors

Andreas Blaette [aut, cre] (<https://orcid.org/0000-0001-8970-8010>), Christoph Leonhardt [ctb]

Initial release

2020-09-22