Stemming words in r does not work as expected - r

Question

I am trying to do a very simple word steming in R and getting something very unexpected. In the code below 'complete' variable is 'NA'. Why can't I complete stem on the word easy?
library(tm)
library(SnowballC)
dict <- c("easy")
stem <- stemDocument(dict, language = "english")
complete <- stemCompletion(stem, dictionary=dict)
Thank You!

Answer 1

You can see the internals of the stemCompletion() function with tm:::stemCompletion.
function (x, dictionary, type = c("prevalent", "first", "longest", "none", "random", "shortest")){
if(inherits(dictionary, "Corpus"))
dictionary <- unique(unlist(lapply(dictionary, words)))
type <- match.arg(type)
possibleCompletions <- lapply(x, function(w) grep(sprintf("^%s",w), dictionary, value = TRUE))
switch(type, first = {
setNames(sapply(possibleCompletions, "[", 1), x)
}, longest = {
ordering <- lapply(possibleCompletions, function(x) order(nchar(x),
decreasing = TRUE))
possibleCompletions <- mapply(function(x, id) x[id],
possibleCompletions, ordering, SIMPLIFY = FALSE)
setNames(sapply(possibleCompletions, "[", 1), x)
}, none = {
setNames(x, x)
}, prevalent = {
possibleCompletions <- lapply(possibleCompletions, function(x) sort(table(x),
decreasing = TRUE))
n <- names(sapply(possibleCompletions, "[", 1))
setNames(if (length(n)) n else rep(NA, length(x)), x)
}, random = {
setNames(sapply(possibleCompletions, function(x) {
if (length(x)) sample(x, 1) else NA
}), x)
}, shortest = {
ordering <- lapply(possibleCompletions, function(x) order(nchar(x)))
possibleCompletions <- mapply(function(x, id) x[id],
possibleCompletions, ordering, SIMPLIFY = FALSE)
setNames(sapply(possibleCompletions, "[", 1), x)
})
}
The x argument is your stemmed terms, dictionary is the unstemmed. The only line that matters is the fifth; it does a simple regex match for the stemmed word in the list of dictionary terms.
possibleCompletions <- lapply(x, function(w) grep(sprintf("^%s",w), dictionary, value = TRUE))
Therefore it fails, since it can't find a match for "easi" with "easy". If you also have the word "easiest" in your dictionary, then both terms match, since there is now a dictionary word with the same beginning four letters to match to.
library(tm)
library(SnowballC)
dict <- c("easy","easiest")
stem <- stemDocument(dict, language = "english")
complete <- stemCompletion(stem, dictionary=dict)
complete
easi easiest
"easiest" "easiest"

Answer 2

wordStem() seems to do it..
library(tm)
library(SnowballC)
dict <- c("easy")
> wordStem(dict)
[1] "easi"