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textstat-class

S4 textstat superclass.

Description

The textstat-class (technically an S4 class) serves as a superclass for the classes features, context, and partition. Usually, the class will not be used directly. It offers a set of standard generic methods (such as head, tail, dim, nrow, colnames) its childs inherit. The core feature of textstat and its childs is a data.table in the slot stat for keeping data on text statistics of a corpus, or a partition.

Usage

## S4 method for signature 'textstat'
name(x)

## S4 method for signature 'character'
name(x)

## S4 replacement method for signature 'textstat'
name(x) <- value

## S4 method for signature 'textstat'
round(x, digits = 2L)

## S4 method for signature 'textstat'
sort(x, by, decreasing = TRUE)

as.bundle(object, ...)

## S4 method for signature 'textstat,textstat'
e1 + e2

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

## S3 method for class 'textstat'
as.data.table(x, ...)

## S4 method for signature 'textstat'
show(object)

## S4 method for signature 'textstat'
p_attributes(.Object)

## S4 method for signature 'textstat'
knit_print(x, options = knitr::opts_chunk, ...)

## S4 method for signature 'textstat'
get_corpus(x)

## S4 method for signature 'textstat'
format(x, digits = 2L)

## S4 method for signature 'textstat'
view(.Object)

Arguments

`x`	A `textstat` object.
`value`	A `character` vector to assign as name to slot `name` of a `textstat` class object.
`digits`	Number of digits.
`by`	Column that will serve as the key for sorting.
`decreasing`	Logical, whether to return decreasing order.
`object`	a textstat object
`...`	Argument that will be passed into a call of the `format` method on the object `x`.
`e1`	A `texstat` object.
`e2`	Another `texstat` object.
`subset`	A logical expression indicating elements or rows to keep.
`.Object`	A `textstat` object.
`options`	Chunk options.

Details

A head-method will return the first rows of the data.table in the stat-slot. Use argument n to specify the number of rows.

A tail-method will return the last rows of the data.table in the stat-slot. Use argument n to specify the number of rows.

The methods dim, nrow and ncol will return information on the dimensions, the number of rows, or the number of columns of the data.table in the stat-slot, respectively.

Objects derived from the textstat class can be indexed with simple square brackets ("[") to get rows specified by an numeric/integer vector, and with double square brackets ("[[") to get specific columns from the data.table in the slot stat.

The colnames-method will return the column names of the data-table in the slot stat.

The methods as.data.table, and as.data.frame will extract the data.table in the slot stat as a data.table, or data.frame, respectively.

textstat objects can have a name, which can be retrieved, and set using the name-method and name<-, respectively.

The round()-method looks up all numeric columns in the data.table in the stat-slot of the textstat object and rounds values of these columns to the number of decimal places specified by argument digits.

The knit_print method will be called by knitr to render 'textstat' objects or objects inheriting from the 'textstat' class as a DataTable htmlwidget when rendering a R Markdown document as html. It will usually be necessary to explicitly state "render = knit_print" in the chunk options. The option 'polmineR.pagelength' controls the number of lines displayed in the resulting 'htmlwidget'. Note that including htmlwidgets in html documents requires that pandoc is installed. To avoid an error, a formatted data.table is returned by knit_print if pandoc is not available.

The format()-method returns a pretty-printed and minimized version of the data.table in the stat-slot of the textstat-object: It will round all numeric columns to the number of decimal numbers specified by digits, and drop all columns with token ids. The return value is a data.table.

Slots

p_attribute: Object of class character, p-attribute of the query.
corpus: A corpus specified by a length-one character vector.
stat: A data.table with statistical information.
name: The name of the object.
annotation_cols: A character vector, column names of data.table in slot stat that are annotations.
encoding: A length-one character vector, the encoding of the corpus.

Examples

use("polmineR")
P <- partition("GERMAPARLMINI", date = ".*", p_attribute = "word", regex = TRUE)
y <- cooccurrences(P, query = "Arbeit")

# generics defined in the polmineR package
x <- count("REUTERS", p_attribute = "word")
name(x) <- "count_reuters"
name(x)
get_corpus(x)

# Standard generic methods known from data.frames work for objects inheriting
# from the textstat class

head(y)
tail(y)
nrow(y)
ncol(y)
dim(y)
colnames(y)

# Use brackets for indexing 

## Not run: 
y[1:25]
y[,c("word", "ll")]
y[1:25, "word"]
y[1:25][["word"]]
y[which(y[["word"]] %in% c("Arbeit", "Sozial"))]
y[ y[["word"]] %in% c("Arbeit", "Sozial") ]

## End(Not run)
sc <- partition("GERMAPARLMINI", speaker = "Angela Dorothea Merkel")
cnt <- count(sc, p_attribute = c("word", "pos"))
cnt_min <- subset(cnt, pos %in% c("NN", "ADJA"))
cnt_min <- subset(cnt, pos == "NE")

# Get statistics in textstat object as data.table
count_dt <- corpus("REUTERS") %>%
  subset(grep("saudi-arabia", places)) %>% 
  count(p_attribute = "word") %>%
  as.data.table()

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