raw_data(type = NULL, file = NULL)(optional) a string indicating the file type of the raw data
(default: NULL).
(optional) a character object indicating the file name(s) of
the raw data (default: NULL).
If type = NULL, a character object with all file type names
available.
If type != NULL and file = NULL, a character object with all file
names available from type.
If type != NULL and file != NULL, a character with the file name(s)
path.
if (FALSE) {
raw_data()
}