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TextReuseTextDocument.R
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TextReuseTextDocument.R
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#' TextReuseTextDocument
#'
#' This is the constructor function for \code{TextReuseTextDocument} objects.
#' This class is used for comparing documents.
#'
#' @param text A character vector containing the text of the document. This
#' argument can be skipped if supplying \code{file}.
#' @param file The path to a text file, if \code{text} is not provided.
#' @param meta A list with named elements for the metadata associated with this
#' document. If a document is created using the \code{text} parameter, then
#' you must provide an \code{id} field, e.g., \code{meta = list(id =
#' "my_id")}. If the document is created using \code{file}, then the ID will
#' be created from the file name.
#' @param tokenizer A function to split the text into tokens. See
#' \code{\link{tokenizers}}. If value is \code{NULL}, then tokenizing and
#' hashing will be skipped.
#' @param ... Arguments passed on to the \code{tokenizer}.
#' @param hash_func A function to hash the tokens. See
#' \code{\link{hash_string}}.
#' @param minhash_func A function to create minhash signatures of the document.
#' See \code{\link{minhash_generator}}.
#' @param keep_tokens Should the tokens be saved in the document that is
#' returned or discarded?
#' @param keep_text Should the text be saved in the document that is returned or
#' discarded?
#' @param skip_short Should short documents be skipped? (See details.)
#'
#' @details This constructor function follows a three-step process. It reads in
#' the text, either from a file or from memory. It then tokenizes that text.
#' Then it hashes the tokens. Most of the comparison functions in this package
#' rely only on the hashes to make the comparison. By passing \code{FALSE} to
#' \code{keep_tokens} and \code{keep_text}, you can avoid saving those
#' objects, which can result in significant memory savings for large corpora.
#'
#' If \code{skip_short = TRUE}, this function will return \code{NULL} for very
#' short or empty documents. A very short document is one where there are two
#' few words to create at least two n-grams. For example, if five-grams are
#' desired, then a document must be at least six words long. If no value of
#' \code{n} is provided, then the function assumes a value of \code{n = 3}. A
#' warning will be printed with the document ID of a skipped document.
#'
#' @return An object of class \code{TextReuseTextDocument}. This object inherits
#' from the virtual S3 class \code{\link[NLP]{TextDocument}} in the NLP
#' package. It contains the following elements: \describe{ \item{content}{The
#' text of the document.} \item{tokens}{The tokens created from the text.}
#' \item{hashes}{Hashes created from the tokens.} \item{minhashes}{The minhash
#' signature of the document.} \item{metadata}{The document metadata,
#' including the filename (if any) in \code{file}.} }
#'
#' @seealso \link[=TextReuseTextDocument-accessors]{Accessors for TextReuse
#' objects}.
#'
#' @examples
#' file <- system.file("extdata/legal/ny1850-match.txt", package = "textreuse")
#' doc <- TextReuseTextDocument(file = file, meta = list(id = "ny1850"))
#' print(doc)
#' meta(doc)
#' head(tokens(doc))
#' head(hashes(doc))
#' \dontrun{
#' content(doc)
#' }
#' @export
TextReuseTextDocument <- function(text, file = NULL, meta = list(),
tokenizer = tokenize_ngrams, ...,
hash_func = hash_string,
minhash_func = NULL,
keep_tokens = FALSE,
keep_text = TRUE,
skip_short = TRUE) {
if (!missing(text)) assert_that(has_id(meta))
if (!is.null(file)) {
assert_that(missing(text),
is.readable(file))
text <- as_string(readLines(file))
}
assert_that(is.character(text))
text <- as_string(text)
# Define document ID early
document_id <- ifelse(is.null(meta$id), filenames(file), meta$id)
# Check length of document
if (skip_short) {
n_call <- match.call(expand.dots = TRUE)[["n"]]
if (is.null(n_call))
n_call <- 3
if (wordcount(text) < n_call + 1) {
warning("Skipping document with ID '", document_id,
"' because it has too few words ",
"to create at least two n-grams with n = ", n_call, ".",
call. = FALSE, noBreaks. = TRUE)
return(NULL)
}
}
# Tokenize and hash
if (!is.null(tokenizer)) {
assert_that(is.function(tokenizer))
tokenizer_name <- as.character(substitute(tokenizer))
tokens <- tokenizer(text, ...)
assert_that(is.function(hash_func))
hash_func_name <- as.character(substitute(hash_func))
hashes <- hash_func(tokens)
# Also minhash if requested
if (!is.null(minhash_func)) {
assert_that(is.function(minhash_func))
minhash_func_name <- as.character(substitute(minhash_func))
minhashes <- minhash_func(tokens)
} else {
minhashes <- NULL
minhash_func_name <- NULL
}
} else {
tokens <- NULL
hashes <- NULL
minhashes <- NULL
tokenizer_name <- NULL
hash_func_name <- NULL
minhash_func_name <- NULL
}
if (!keep_tokens) tokens <- NULL
if (!keep_text) text <- NULL
if (missing(meta)) {
meta <- list(file = file,
id = document_id,
tokenizer = tokenizer_name,
hash_func = hash_func_name,
minhash_func = minhash_func_name)
}
assert_that(is.list(meta))
if (!is.null(file)) {
meta$file <- file
meta$id <- document_id
}
# Don't overwrite these when called from TextReuseCorpus
if (is.null(meta$tokenizer) & is.null(meta$hash_func) &
is.null(meta$minhash_func)) {
meta$tokenizer <- tokenizer_name
meta$hash_func <- hash_func_name
meta$minhash_func <- minhash_func_name
}
meta <- sort_meta(meta)
doc <- list(
content = text,
tokens = tokens,
hashes = hashes,
minhashes = minhashes,
meta = meta
)
class(doc) <- c("TextReuseTextDocument", "TextDocument")
doc
}
#' @importFrom NLP meta
#' @export
NLP::meta
#' @importFrom NLP meta<-
#' @export
NLP::`meta<-`
#' @importFrom NLP content
#' @export
NLP::content
#' @importFrom NLP content<-
#' @export
NLP::`content<-`
#' @export
print.TextReuseTextDocument <- function(x, ...) {
cat("TextReuseTextDocument\n")
pretty_print_metadata(x)
cat("content", ":", str_sub(x$content, end = 200))
invisible(x)
}
#' @export
as.character.TextReuseTextDocument <- function(x, ...) {
as.character(x$content)
}
#' @export
#' @method content TextReuseTextDocument
content.TextReuseTextDocument <- function(x) {
x$content
}
#' @export
#' @method content<- TextReuseTextDocument
`content<-.TextReuseTextDocument` <- function(x, value) {
assert_that(is.character(value))
x$content <- value
x
}
#' @export
#' @method meta TextReuseTextDocument
meta.TextReuseTextDocument <- function(x, tag = NULL, ...) {
if (is.null(tag))
x$meta
else
x$meta[[tag]]
}
#' @export
#' @method meta<- TextReuseTextDocument
`meta<-.TextReuseTextDocument` <- function(x, tag = NULL, ..., value) {
if (is.null(tag)) {
assert_that(is.list(value))
x$meta <- value
} else {
x$meta[[tag]] <- value
}
x
}
#' Accessors for TextReuse objects
#'
#' Accessor functions to read and write components of
#' \code{\link{TextReuseTextDocument}} and \code{\link{TextReuseCorpus}}
#' objects.
#' @name TextReuseTextDocument-accessors
#' @param x The object to access.
#' @param value The value to assign.
#' @return Either a vector or a named list of vectors.
NULL
#' @export
#' @rdname TextReuseTextDocument-accessors
tokens <- function(x) UseMethod("tokens", x)
#' @export
tokens.TextReuseTextDocument <- function(x) x$tokens
#' @export
tokens.TextReuseCorpus <- function(x) {
corpus_names <- names(x)
l <- lapply(x$documents, function(i) tokens(i))
names(l) <- corpus_names
l
}
#' @export
#' @rdname TextReuseTextDocument-accessors
`tokens<-` <- function(x, value) UseMethod("tokens<-", x)
#' @export
`tokens<-.TextReuseTextDocument` <- function(x, value) {
x$tokens <- value
x
}
#' @export
#' @rdname TextReuseTextDocument-accessors
hashes <- function(x) UseMethod("hashes", x)
#' @export
hashes.TextReuseTextDocument <- function(x) x$hashes
#' @export
hashes.TextReuseCorpus <- function(x) {
corpus_names <- names(x)
l <- lapply(x$documents, function(i) hashes(i))
names(l) <- corpus_names
l
}
#' @export
#' @rdname TextReuseTextDocument-accessors
`hashes<-` <- function(x, value) UseMethod("hashes<-", x)
#' @export
`hashes<-.TextReuseTextDocument` <- function(x, value) {
x$hashes <- value
x
}
#' @export
#' @rdname TextReuseTextDocument-accessors
minhashes <- function(x) UseMethod("minhashes", x)
#' @export
minhashes.TextReuseTextDocument <- function(x) x$minhashes
#' @export
minhashes.TextReuseCorpus <- function(x) {
corpus_names <- names(x)
l <- lapply(x$documents, function(i) minhashes(i))
names(l) <- corpus_names
l
}
#' @export
#' @rdname TextReuseTextDocument-accessors
`minhashes<-` <- function(x, value) UseMethod("minhashes<-", x)
#' @export
`minhashes<-.TextReuseTextDocument` <- function(x, value) {
x$minhashes <- value
x
}
#' @param x An R object to check.
#' @export
#' @rdname TextReuseTextDocument
is.TextReuseTextDocument <- function(x) {
inherits(x, "TextReuseTextDocument")
}
#' @export
#' @rdname TextReuseTextDocument
has_content <- function(x) {
assert_that(is.TextReuseTextDocument(x))
!is.null(x$content)
}
assertthat::on_failure(has_content) <- function(call, env) {
paste0("Document does not have text in its content field.")
}
#' @export
#' @rdname TextReuseTextDocument
has_tokens <- function(x) {
assert_that(is.TextReuseTextDocument(x))
!is.null(x$tokens)
}
assertthat::on_failure(has_tokens) <- function(call, env) {
"Document does not have tokens."
}
#' @export
#' @rdname TextReuseTextDocument
has_hashes <- function(x) {
assert_that(is.TextReuseTextDocument(x))
!is.null(x$hashes)
}
assertthat::on_failure(has_hashes) <- function(call, env) {
"Document does not have hashes."
}
#' @export
#' @rdname TextReuseTextDocument
has_minhashes <- function(x) {
assert_that(is.TextReuseTextDocument(x))
!is.null(x$minhashes)
}
assertthat::on_failure(has_minhashes) <- function(call, env) {
"Document does not have a minhash signature."
}
has_minhashes_corpus <- function(x) {
assert_that(is.TextReuseCorpus(x))
all(vapply(minhashes(x), Negate(is.null), logical(1)))
}
assertthat::on_failure(has_minhashes_corpus) <- function(call, env) {
"Some documents in the corpus do not have a minhash signature."
}