inst/doc/textrank.R

In textrank: Summarize Text by Ranking Sentences and Finding Keywords

## ----setup, include=FALSE, cache=FALSE------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
options(width = 1000)
knitr::opts_chunk$set(echo = TRUE, message = FALSE, comment = NA, eval = (require(udpipe) & require(textreuse)))

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
library(textrank)
data(joboffer)
cat(unique(joboffer$sentence), sep = "\n")

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
head(joboffer[, c("sentence_id", "lemma", "upos")], 10)

## ---- eval=FALSE----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
#  job_rawtxt <- readLines(system.file(package = "textrank", "extdata", "joboffer.txt"))
#  job_rawtxt <- paste(job_rawtxt, collapse = "\n")
#  
#  library(udpipe)
#  tagger <- udpipe_download_model("english")
#  tagger <- udpipe_load_model(tagger$file_model)
#  joboffer <- udpipe_annotate(tagger, job_rawtxt)
#  joboffer <- as.data.frame(joboffer)

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
keyw <- textrank_keywords(joboffer$lemma,
                          relevant = joboffer$upos %in% c("NOUN", "VERB", "ADJ"))
subset(keyw$keywords, ngram > 1 & freq > 1)

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
head(joboffer[, c("sentence_id", "lemma", "upos")], 10)

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
library(udpipe)
joboffer$textrank_id <- unique_identifier(joboffer, c("doc_id", "paragraph_id", "sentence_id"))
sentences <- unique(joboffer[, c("textrank_id", "sentence")])
terminology <- subset(joboffer, upos %in% c("NOUN", "ADJ"))
terminology <- terminology[, c("textrank_id", "lemma")]
head(terminology)

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
## Textrank for finding the most relevant sentences
tr <- textrank_sentences(data = sentences, terminology = terminology)
names(tr)
plot(sort(tr$pagerank$vector, decreasing = TRUE), 
     type = "b", ylab = "Pagerank", main = "Textrank")

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
s <- summary(tr, n = 4)
s <- summary(tr, n = 4, keep.sentence.order = TRUE)
cat(s, sep = "\n")

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
## Limit the number of candidates with the minhash algorithm
library(textreuse)
minhash <- minhash_generator(n = 1000, seed = 123456789)
candidates <- textrank_candidates_lsh(x = terminology$lemma, 
                                      sentence_id = terminology$textrank_id,
                                      minhashFUN = minhash, 
                                      bands = 500)
dim(candidates)
head(candidates)

## -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
tr <- textrank_sentences(data = sentences, terminology = terminology, textrank_candidates = candidates)
s <- summary(tr, n = 4, keep.sentence.order = TRUE)
cat(s, sep = "\n")