Package tm: removeWords How do I avoid removing CERTIAN (negations specifically) "english" stopwords if specified?

Question

I would like to use the removeWords (stopwords("english")) function via: corpus <- tm_map(corpus,removeWords, stopwords("english")) but some words like "not", and other negations I'd like to keep.

Is it possible to use the removeWords, stopwords("english") function BUT exclude certain words in that list if specified?

How could I prevent the removal of "not" for example?

(Secondary) is it possible to set this type of control list to all "negations"?

I'd rather not resort to creating my own custom list with only the words from that stoplist that I'm interested in.

Answer 1

You can create a custom list of stopwords by taking the difference between stopwords("en") and the list of words you want to exclude:

exceptions   <- c("not")
my_stopwords <- setdiff(stopwords("en"), exceptions)

If you need to remove all the negations, you can grep them from the stopwords() list:

exceptions <- grep(pattern = "not|n't", x = stopwords(), value = TRUE)
# [1] "isn't"     "aren't"    "wasn't"    "weren't"   "hasn't"    "haven't"   "hadn't"    "doesn't"   "don't"     "didn't"   
# [11] "won't"     "wouldn't"  "shan't"    "shouldn't" "can't"     "cannot"    "couldn't"  "mustn't"   "not"
my_stopwords <- setdiff(stopwords("en"), exceptions)