docvars: Get or set document-level variables

In koheiw/quanteda.core: Quantitative Analysis of Textual Data

Description

Get or set variables associated with a document in a corpus, tokens or dfm object.

Usage

docvars(x, field = NULL)

docvars(x, field = NULL) <- value

## S3 method for class 'corpus'
x$name

## S3 replacement method for class 'corpus'
x$name <- value

## S3 method for class 'tokens'
x$name

## S3 replacement method for class 'tokens'
x$name <- value

## S3 method for class 'dfm'
x$name

## S3 replacement method for class 'dfm'
x$name <- value

Arguments

x	corpus, tokens, or dfm object whose document-level variables will be read or set
field	string containing the document-level variable name
value	a vector of document variable values to be assigned to name
name	a literal character string specifying a single docvars name

Value

docvars returns a data.frame of the document-level variables, dropping the second dimension to form a vector if a single docvar is returned.

docvars<- assigns value to the named field

Accessing or assigning docvars using the $ operator

As of quanteda v2, it is possible to access and assign a docvar using the $ operator. See Examples.

Note

Reassigning document variables for a tokens or dfm object is allowed, but discouraged. A better, more reproducible workflow is to create your docvars as desired in the corpus, and let these continue to be attached "downstream" after tokenization and forming a document-feature matrix. Recognizing that in some cases, you may need to modify or add document variables to downstream objects, the assignment operator is defined for tokens or dfm objects as well. Use with caution.

Examples

# retrieving docvars from a corpus
head(docvars(data_corpus_inaugural))
tail(docvars(data_corpus_inaugural, "President"), 10)
head(data_corpus_inaugural$President)

# assigning document variables to a corpus
corp <- data_corpus_inaugural
docvars(corp, "President") <- paste("prez", 1:ndoc(corp), sep = "")
head(docvars(corp))
corp$fullname <- paste(data_corpus_inaugural$FirstName,
                       data_corpus_inaugural$President)
tail(corp$fullname)


# accessing or assigning docvars for a corpus using "$"
data_corpus_inaugural$Year
data_corpus_inaugural$century <- floor(data_corpus_inaugural$Year / 100)
data_corpus_inaugural$century

# accessing or assigning docvars for tokens using "$"
toks <- tokens(corpus_subset(data_corpus_inaugural, Year <= 1805))
toks$Year
toks$Year <- 1991:1995
toks$Year
toks$nonexistent <- TRUE
docvars(toks)

# accessing or assigning docvars for a dfm using "$"
dfmat <- dfm(toks)
dfmat$Year
dfmat$Year <- 1991:1995
dfmat$Year
dfmat$nonexistent <- TRUE
docvars(dfmat)

koheiw/quanteda.core documentation built on Sept. 21, 2020, 3:44 p.m.