The result of no stemming with 15% of data.  No improvement in hitting on quiz answers.

Munging data
 Running preprocessing script: 00-init.R
 Running preprocessing script: 01-lines.R
creating data set: lines @ 2014-11-06 21:22:58
sampling 15% of original data
saving to cache: lines [character] @ 2014-11-06 21:24:29
allocating 95% for training data
creating data set: train.lines @ 2014-11-06 21:24:29
saving to cache: train.lines [character] @ 2014-11-06 21:24:38
creating data set: test.lines @ 2014-11-06 21:24:38
saving to cache: test.lines [character] @ 2014-11-06 21:24:48
 Running preprocessing script: 02-corpus.R
creating data set: train.corpus @ 2014-11-06 21:24:49
saving to cache: train.corpus [VCorpus Corpus] @ 2014-11-06 21:34:49
 Running preprocessing script: 03-tdm.R
creating data set: train.tdm @ 2014-11-06 21:34:53
saving to cache: train.tdm [TermDocumentMatrix simple_triplet_matrix] @ 2014-11-06 22:15:12
 Running preprocessing script: 04-model.R
creating data set: model @ 2014-11-06 22:15:12
saving to cache: model [data.table data.frame] @ 2014-11-06 22:30:32
 Running preprocessing script: 05-test-phrases.R
creating data set: test.phrases @ 2014-11-06 22:30:32
The ngram model predicted 13% accurately.
The null model predicted 4.25% accurately.
saving to cache: test.phrases [data.table data.frame] @ 2014-11-06 23:07:20
There were 50 or more warnings (use warnings() to see the first 50)