Try to improve the text cleaning in find Msg Words () of Section 3.5.3 by stemming the words in the messages. That is, make plural words singular and reduce present and past tenses to their root words, e.g., run, ran, runs, running all have the same "stem." To do this, use the stemming functions available in the text mining package tm. Incorporate this stemming process into the find Msg Words () function. Then recreate the vectors of words for all the email and see if the classification improves.