r - 使用R将PDF文件转换为文本文件以进行文本挖掘

Question

我的文件夹中有近一千篇pdf期刊文章。我需要从整个文件夹中的所有文章摘要中获取文本信息。现在，我正在执行以下操作：

dest <- "~/A1.pdf"

# set path to pdftotxt.exe and convert pdf to text
exe <- "C:/Program Files (x86)/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)

这样，我将一个pdf文件转换为一个.txt文件，然后将摘要复制到另一个.txt文件中，并手动进行编译。这项工作很麻烦。

如何读取文件夹中的所有文章并将其转换为.txt文件，其中仅包含每篇文章的摘要。可以通过限制每篇文章的摘要和简介之间的内容来完成；但我无法这样做。任何帮助表示赞赏。

Answer 1

是的，实际上不是IShouldBuyABoat所指出的R问题，而是R可以通过很小的扭曲就可以解决的问题...

使用R将PDF文件转换为txt文件...

# folder with 1000s of PDFs
dest <- "C:\\Users\\Desktop"

# make a vector of PDF file names
myfiles <- list.files(path = dest, pattern = "pdf",  full.names = TRUE)

# convert each PDF file that is named in the vector into a text file 
# text file is created in the same directory as the PDFs
# note that my pdftotext.exe is in a different location to yours
lapply(myfiles, function(i) system(paste('"C:/Program Files/xpdf/bin64/pdftotext.exe"', 
             paste0('"', i, '"')), wait = FALSE) )

仅从txt文件中提取摘要...

# if you just want the abstracts, we can use regex to extract that part of
# each txt file, Assumes that the abstract is always between the words 'Abstract'
# and 'Introduction'
mytxtfiles <- list.files(path = dest, pattern = "txt",  full.names = TRUE)
abstracts <- lapply(mytxtfiles, function(i) {
  j <- paste0(scan(i, what = character()), collapse = " ")
  regmatches(j, gregexpr("(?<=Abstract).*?(?=Introduction)", j, perl=TRUE))
})

将摘要写入单独的txt文件...

# write abstracts as txt files 
# (or use them in the list for whatever you want to do next)
lapply(1:length(abstracts),  function(i) write.table(abstracts[i], file=paste(mytxtfiles[i], "abstract", "txt", sep="."), quote = FALSE, row.names = FALSE, col.names = FALSE, eol = " " ))

现在，您可以对摘要进行一些文本挖掘了。