grouping.var: The grouping variables. Default NULL generates one word list for all text. Also takes a single grouping variable or a list of 1 or more grouping variables.
n.words: An integer specifying the number of words in each chunk.
``: ignored.
Returns
Returns a list of class type_text_ratio. This object contains a type-token ratio for the overall text and a data frame type-token ratios per grouping vriable.