How to use OpenNLP to get POS tags in R?

Question

Here is the R Code:

library(NLP) 
library(openNLP)
tagPOS <-  function(x, ...) {
s <- as.String(x)
word_token_annotator <- Maxent_Word_Token_Annotator()
a2 <- Annotation(1L, "sentence", 1L, nchar(s))
a2 <- annotate(s, word_token_annotator, a2)
a3 <- annotate(s, Maxent_POS_Tag_Annotator(), a2)
a3w <- a3[a3$type == "word"]
POStags <- unlist(lapply(a3w$features, `[[`, "POS"))
POStagged <- paste(sprintf("%s/%s", s[a3w], POStags), collapse = " ")
list(POStagged = POStagged, POStags = POStags)}
str <- "this is a the first sentence."
tagged_str <-  tagPOS(str)

Output is :

tagged_str $POStagged [1]"this/DT is/VBZ a/DT the/DT first/JJ sentence/NN ./."

Now I want to extract only NN word i.e sentence from the above sentence and want to store it into a variable .Can anyone help me out with this .

Answer 1

There might be more elegant ways to obtain the result, but this one should work:

q <- strsplit(unlist(tagged_str[1]),'/NN')
q <- tail(strsplit(unlist(q[1])," ")[[1]],1)
#> q
#[1] "sentence"

Hope this helps.