Convert an eligible input object into a dfm, or check whether an object is a dfm. Current eligible inputs for coercion to a dfm are: matrix, (sparse) Matrix, TermDocumentMatrix and DocumentTermMatrix (from the tm package), data.frame, and other dfm objects.
a candidate object for checking or coercion to dfm
as.dfm converts an input object into a dfm. Row names
are used for docnames, and column names for featnames, of the resulting
TRUE if and only if its argument is a dfm.