使用readPDF在R (tm包)

Question

我是R的初学者，使用tm包有点麻烦。我需要从第55页到第300页提取特定的数据，并认为R可能是一个很好的方法。(如果有人有更好的主意，请告诉我!)我做了一些搜索，在安装了tm包和xpdf包之后，我试着阅读这篇文章，并尝试了zx8754的解决方案，但没有运气。我怀疑它与readPDF命令有关——我得到以下内容:

readPDF(PdftotextOptions = "-layout")错误:未使用的参数(pdftotextopoptions = "-layout")

我认为这与尝试使用tm包和xpdf包在一起有关，所以我读了托尼布雷亚尔的解决方案(我不能发布超过2个链接)，把pdfinfo和pdftotext作为环境变量(我在Win 8上)并重新启动。我确信我错过了一些东西-现在我在r中的工作目录中有pdftotext.exe，谁能帮助我正确配置这个，以便tm包正确调用xpdf文件并像它应该的那样读取pdf函数?

再次强调，我对这个很陌生，所以如果我说的有点离题，我很抱歉。如果你能帮助我，我将不胜感激。

提前感谢，

贾斯汀

Answer 1

为了让您入门，这里有一个完整的readPDF命令示例，用于读取PDF文件。当我试图从您提供的链接直接检索PDF文件时，readPDF抛出了一个错误，所以我先将PDF文件下载到我的工作目录。

library(tm)
# File name
filename = "ea0607.pdf"
# Read the PDF file
doc <- readPDF(control = list(text = "-layout"))(elem = list(uri = filename),
                                                 language = "en",
                                                 id = "id1")

上面的代码将PDF文件转换为文本并将结果存储在doc中。doc实际上是一个列表，如下面的代码所示:

str(doc)
List of 2
 $ content: chr [1:23551] "  STATE UNIVERSITY SYSTEM OF FLORIDA" "" "EXPENDITURE ANALYSIS" "      2006-2007" ...
 $ meta   :List of 7
  ..$ author       : chr "greg.jacques"
  ..$ datetimestamp: POSIXlt[1:1], format: "2007-12-10 11:33:48"
  ..$ description  : NULL
  ..$ heading      : chr " PGM=EASUSI-V01                                        STATE UNIVERSITY SYSTEM                                                 "| __truncated__
  ..$ id           : chr "ea0607.pdf"
  ..$ language     : chr "en"
  ..$ origin       : chr "Acrobat PDFMaker 8.1 for Word"
  ..- attr(*, "class")= chr "TextDocumentMeta"
 - attr(*, "class")= chr [1:2] "PlainTextDocument" "TextDocument"

PDF文件的文本存储在doc$content中，而doc$meta包含PDF文件的各种元数据。doc$content的每一行都是PDF文件中的一行。以下是PDF文件的第300至310行:

doc$content[300:310]
 [1] ""                                                                                                                      
 [2] "and General (E&G) budget entity. The Expenditure Analysis continues to reflect special units separately and the"       
 [3] ""                                                                                                                      
 [4] "traditional program components and related activities have been further defined to support the funding formula. The"   
 [5] ""                                                                                                                      
 [6] "Expenditure Analysis format was revised in 1995-96 to include all activities in the funding formula as well as college"
 [7] ""                                                                                                                      
 [8] "detail by activity for the UF Health Science Center, the USF Health Science Center and the FSU Medical School. A"      
 [9] ""                                                                                                                      
[10] "definition of each follows:"                                                                                           
[11] ""