Help: stemming and stem completion with package tm in R

November 3, 2011

(This article was first published on RDataMining, and kindly contributed to R-bloggers)

I came across a problem below when doing stemming and stem completion with package tm in R. Word “mining” was stemmed to “mine” with stemDocument(), and then completed to “miners”with stemCompletion(). However, I prefer to keep “mining” intact.

For stemCompletion(), the default type of completion is “prevalent”, which takes the most frequent match as completion. Although “mining” is much more frequent than “miners” in my text, it still completed “mine” to “miners”.

An example is shown below.

############################################
library(tm)
(a <- c("mining", "miners", "mining"))
(b <- stemDocument(a))
(d <- stemCompletion(b, dictionary=a))
############################################

Some possible solutions are:
1) to change the options or dictionary in stemDocument(), so that "mining" is not stemmed to "mine", which I think is the best way;
2) to change the options or dictionary in stemCompletion(), so that "mine" is completed to "mining";
3) to manually correct this after stem completion, which is the last option.

I am looking for a solution for above 1) or 2), but cannot find the way to do it with stemDocument() in package tm.

Any help will be appreciated.

Thanks,
Yanchang Zhao
Email: yanchangzhao(at)gmail.com

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