Creating readers.
getReaders()For getReaders(), a character vector with readers provided by package
tm.
Readers are functions for extracting textual content and metadata out
of elements delivered by a Source, and for constructing a
TextDocument. A reader must accept following arguments in
its signature:
elema named list with the components content and
uri (as delivered by a Source via
getElem or pGetElem).
languagea character string giving the language.
ida character giving a unique identifier for the created text document.
The element elem is typically provided by a source whereas the language
and the identifier are normally provided by a corpus constructor (for the case
that elem$content does not give information on these two essential
items).
In case a reader expects configuration arguments we can use a function
generator. A function generator is indicated by inheriting from class
FunctionGenerator and function. It allows us to process
additional arguments, store them in an environment, return a reader function
with the well-defined signature described above, and still be able to access
the additional arguments via lexical scoping. All corpus constructors in
package tm check the reader function for being a function generator and
if so apply it to yield the reader with the expected signature.
readDOC, readPDF, readPlain,
readRCV1, readRCV1asPlain,
readReut21578XML, readReut21578XMLasPlain,
readTabular, and readXML.