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# Author: Ingo Feinerer
TextDocumentMeta <-
function(author, datetimestamp, description, heading, id, language, origin, ...,
meta = NULL)
{
if (is.null(meta))
meta <- list(author = author, datetimestamp = datetimestamp,
description = description, heading = heading, id = id,
language = language, origin = origin, ...)
stopifnot(is.list(meta))
if (!is.null(meta$author) && !inherits(meta$author, "person"))
meta$author <- as.character(meta$author)
if (!is.null(meta$datetimestamp) && !inherits(meta$datetimestamp, "POSIXt"))
meta$datetimestamp <- as.character(meta$datetimestamp)
if (!is.null(meta$description))
meta$description <- as.character(meta$description)
if (!is.null(meta$heading))
meta$heading <- as.character(meta$heading)
if (!is.null(meta$id))
meta$id <- as.character(meta$id)
if (!is.null(meta$language))
meta$language <- as.character(meta$language)
if (!is.null(meta$origin))
meta$origin <- as.character(meta$origin)
class(meta) <- "TextDocumentMeta"
meta
}
print.TextDocumentMeta <-
function(x, ...)
{
cat(sprintf(" %s: %s",
format(names(x), justify = "left"),
sapply(x, as.character)),
sep = "\n")
invisible(x)
}
CorpusMeta <-
function(..., meta = NULL)
{
if (is.null(meta))
meta <- list(...)
stopifnot(is.list(meta))
class(meta) <- "CorpusMeta"
meta
}
meta.SimpleCorpus <-
function(x, tag = NULL, type = c("indexed", "corpus"), ...)
{
if (identical(tag, "id")) {
n <- names(content(x))
return(if (is.null(n)) as.character(seq_along(x)) else n)
}
if (!is.null(tag) && missing(type))
type <- if (tag %in% names(x$meta)) "corpus" else "indexed"
type <- match.arg(type)
if (identical(type, "indexed"))
if (is.null(tag)) x$dmeta else x$dmeta[tag]
else if (identical(type, "corpus"))
if (is.null(tag)) x$meta else x$meta[[tag]]
else
stop("invalid type")
}
meta.VCorpus <- meta.PCorpus <-
function(x, tag = NULL, type = c("indexed", "corpus", "local"), ...)
{
if (!is.null(tag) && missing(type)) {
type <- if (tag %in% names(x$dmeta)) "indexed"
else if (tag %in% names(x$meta)) "corpus"
else "local"
}
type <- match.arg(type)
if (identical(type, "indexed"))
if (is.null(tag)) x$dmeta else x$dmeta[tag]
else if (identical(type, "corpus"))
if (is.null(tag)) x$meta else x$meta[[tag]]
else if (identical(type, "local"))
lapply(x, meta, tag)
else
stop("invalid type")
}
`meta<-.SimpleCorpus` <-
function(x, tag, type = c("indexed", "corpus"), ..., value)
{
type <- match.arg(type)
if (identical(type, "indexed"))
x$dmeta[, tag] <- value
else if (type == "corpus")
x$meta[[tag]] <- value
else
stop("invalid type")
x
}
`meta<-.VCorpus` <- `meta<-.PCorpus` <-
function(x, tag, type = c("indexed", "corpus", "local"), ..., value)
{
type <- match.arg(type)
if (identical(type, "indexed"))
x$dmeta[, tag] <- value
else if (type == "corpus")
x$meta[[tag]] <- value
else if (identical(type, "local")) {
for (i in seq_along(x))
meta(x[[i]], tag) <- value[i]
} else
stop("invalid type")
x
}
# Simple Dublin Core to tm metadata mapping
# http://en.wikipedia.org/wiki/Dublin_core#Simple_Dublin_Core
Dublin_Core_tm_map <-
list("contributor" = "contributor",
"coverage" = "coverage",
"creator" = "author",
"date" = "datetimestamp",
"description" = "description",
"format" = "format",
"identifier" = "id",
"language" = "language",
"publisher" = "publisher",
"relation" = "relation",
"rights" = "rights",
"source" = "source", # or better "origin"?
"subject" = "subject",
"title" = "heading",
"type" = "type"
)
DublinCore <-
function(x, tag = NULL)
{
tmm <- unlist(Dublin_Core_tm_map, use.names = FALSE)
dcm <- names(Dublin_Core_tm_map)
if (is.null(tag)) {
m <- lapply(tmm, function(t) meta(x, t))
names(m) <- dcm
class(m) <- "TextDocumentMeta"
m
} else
meta(x, tmm[charmatch(tolower(tag), dcm)])
}
`DublinCore<-` <-
function(x, tag, value)
{
tmm <- unlist(Dublin_Core_tm_map, use.names = FALSE)
dcm <- names(Dublin_Core_tm_map)
meta(x, tmm[charmatch(tolower(tag), dcm)]) <- value
x
}
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