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Reading and Text Mining a PDF-File in R

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Reading and Text Mining a PDF-File in R

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Here is an R-script that reads a PDF-file to R and does some text mining with it:

# here is a pdf for mining
url <- "http://www.noisyroom.net/blog/RomneySpeech072912.pdf"
dest <- tempfile(fileext = ".pdf")
download.file(url, dest, mode = "wb")

# set path to pdftotxt.exe and convert pdf to text
exe <- "C:\\Program Files\\xpdfbin-win-3.03\\bin32\\pdftotext.exe"
system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = F)

# get txt-file name and open it
filetxt <- sub(".pdf", ".txt", dest)
shell.exec(filetxt); shell.exec(filetxt) # strangely the first try always throws an error..

# do something with it, i.e. a simple word cloud
library(tm)
library(wordcloud)
library(Rstem)

txt <- readLines(filetxt) # don't mind warning..

txt <- tolower(txt)
txt <- removeWords(txt, c("\\f", stopwords()))

corpus <- Corpus(VectorSource(txt))
corpus <- tm_map(corpus, removePunctuation)
tdm <- TermDocumentMatrix(corpus)
m <- as.matrix(tdm)
d <- data.frame(freq = sort(rowSums(m), decreasing = TRUE))

# Stem words
d$stem <- wordStem(row.names(d), language = "english")

# and put words to column, otherwise they would be lost when aggregating
d$word <- row.names(d)

# remove web address (very long string):
d <- d[nchar(row.names(d)) < 20, ]

# aggregate freqeuncy by word stem and
# keep first words..
agg_freq <- aggregate(freq ~ stem, data = d, sum)
agg_word <- aggregate(word ~ stem, data = d, function(x) x[1])

d <- cbind(freq = agg_freq[, 2], agg_word)

# sort by frequency
d <- d[order(d$freq, decreasing = T), ]

# print wordcloud:
wordcloud(d$word, d$freq)

# remove files
file.remove(dir(tempdir(), full.name=T)) # remove files

 

Hortonworks Sandbox for HDP and HDF is your chance to get started on learning, developing, testing and trying out new features. Each download comes preconfigured with interactive tutorials, sample data and developments from the Apache community.

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