[R] "Complex?" import of pdf files (criminal records) into R table

Marc Schwartz marc_schwartz at me.com
Thu Oct 15 16:28:47 CEST 2009

On Oct 15, 2009, at 3:43 AM, Biedermann, Jürgen wrote:

> Hi there,
> I'm facing the decision if it would be possible to transform several  
> more or less complex pdf files into an R Table-Format or if it has  
> to be done manually. I think it would be a impudent to expect a  
> complete solution, but I would be grateful if anyone could give me  
> an advice on how the structure of such a R-program could look like,  
> and if it's possible in general.
> Here the problem:
> Each pdf file belongs to a person. The pdf files actually represent  
> the anonymous criminal record of a person. Each entry should lead to  
> one row with the person number as key. The different lines should  
> form the columns. The criminal record actually looks like this:
> ---------------------------------------------------
> Header with irrelevant text for us   |  Date: xx.xx.xxxx (relevant  
> for us)
> Anonymous person number: xxxxxxxxxxx
> Entries in the register
> 1. xx.xx.1902  -City-
>   Be in force since: xx.xx.1902
>   Date of offense:xx.xx.xxxx
>   Elements of the offence: For example "Rape"
>   Section in law: §176, §178 Abs. 1
>   Sentenced to 5 years imprisonment
>   "Irrelevant text for us"
>   Accommodation in an forensic psychiatry
>   Accommodation sentenced on probation
>   Rest of sentence sentenced on probation until the xx.xx.xxxx
> 2. xx.xx.1910
>   Be in force since: ....
>   .....
> -----------------------------------------------------------------------
> The problem is that the entries do not always have the same  
> structure. The first 6 lines are structurally the same in each entry  
> of the criminal record (each entry has a line for the judgement  
> date, the "be in force" date, the date of offence, the elements of  
> the offence, the Sections in law, and the sentence).
> But then depending on the sentence different lines emerge which  
> contain information if the person was sentenced on probation, if the  
> probation was withdrawn again, when the person was released etc.
> So, I think, these lines should be allocated to different columns  
> depending on key words. The definition of the key words for most  
> cases would not be the problem, actually. If a certain column is not  
> relevant in an entry (so, the key word didn't emerge) NA should be  
> put in the place.
> But because sometimes (in rare cases), the entries contain spelling  
> errors, at the end, all the lines of an entry, which could not be  
> allocated to a column should be put in a column to check them  
> manually.
> In the end the table should look more of less like this.
> --------------------------------------------------
> "Per 
> .Numb";"EntryNumber";"Judg.Date";"DateOffen.";...;"Probation.until";  
> "Released";"Not allocated"
> xxxx1   1   xx.xx.1902  xx.xx.1901 ... xx.xx.1905 NA  "blablabla"
> xxxx1   2   xx.xx.1910  xx.xx.1909 ... NA        1925  "blablabla"
> xxxx2   1   xx.xx.1924  xx.xx.1923 ... NA        NA  "blablabla"
> ------------------------------------------------------------------
> Could anyone help me?
> Thanks
> Greetings
> Jürgen

You don't indicate the OS you are on, but you will want to get a hold  
of 'pdftotext', which is a command line application that can extract  
the textual content from the PDF files. On most Linuxen, it is already  
installed, but for Windows and OSX you will likely need to Google for  

The basic approach is to loop over each PDF file, use pdftotext to get  
the text content and dump it into a regular text file. That file can  
then be read into R using ?readLines.

This can all be done within R using the ?system command. Get the names  
of the PDF files in a given folder by using ?list.files with a "\ 
\.pdf" or "\\.PDF" search pattern. Then ?paste together the full  
command using a prefix along the lines of "pdftotext -layout - 
nopgbrk", presuming that the pdftotext command is in your $PATH. The  
suffix to be paste()d will be the name of the input PDF file and the  
name of the output text file. So you end up with a command line  
character vector along the lines of:

   "pdftotext -layout -nopgbrk xxxxx.pdf xxxxx.txt"

where the x's are the specific file basenames. Review the pdftotext  
options to understand what is being done and if you should need to  
modify them for your particular files.

Once you have the data in R for each file, you will then need to  
process the content line by line, looking for the keywords that are  
associated with the content you require. Using ?grep is perhaps the  
easiest way to accomplish that. You can then use ?gsub to replace/ 
strip the keywords, leaving you with the data only, for each line. For  
multi line scenarios, you will need to keep track of where the keyword  
for the first line is and then look for the subsequent keyword or  
perhaps a blank line, to know when to stop aggregating the data for  
that initial keyword.

It then becomes a matter of reorganizing the content that you need  
into the format you require for subsequent work.

I have not looked for 'text processing' related packages on CRAN, so  
you may wish to look there first in case there is anything relevant.


Marc Schwartz

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