从包含电子邮件的PDF中提取名称

Question

I have a very specific question. I have a set of PDF files that contain emails (and email chains) and are generally of the following format:

From: Doe, John <john.doe@mail.com>
To: Doe, Jane <john.doe@mail.com>; Doe, John
Subject: Re: Title
text ...
...
From: Doe, John <john.doe@mail.com>
To: Doe, Jane <john.doe@mail.com>; Doe, John
CC: Moe, James; Klein, John
Subject: Title
text ...

So, in one PDF file, you generally have several "from", "to" and "cc" blocks. The format of the names is always that last name and first name are seperated by a comma. Different names are separated by a semi colon. However, sometimes the full email address (which I do not need) will be included between "<" and ">". I would like to extract all of the names (in the from, to, and cc parts) from these PDF files and in the end have output that looks like this:

Last name    first name
Doe          John
Doe          Jane
Moe          James
Klein        John

I have managed to read in the PDF files using the pdftools package:

files <- list.files(pattern = "pdf$")
pdfs <- lapply(files, pdf_text)

However, I am currently a bit stuck in trying to find the best way to extract all of the names and save them in a data frame. I have been looking at the str_extract function: eg starting with str_extract(pdfs[[1]], regex("From.*To", ignore_case = TRUE)) , but haven't been able to find a working solution. Any help would be much appreciated. As an example, assume that pdfs[[1]] contains the following string:

teststring <- "From: Doe, John <john.doe@mail.com>\r\n
To: Doe, Jane <john.doe@mail.com>; Doe, John\r\n
Subject: Re: Title\r\n
text ...\r\n
...\r\n
From: Doe, John <john.doe@mail.com>\r\n
To: Doe, Jane <john.doe@mail.com>; Doe, John\r\n
CC: Moe, James; Klein, John\r\n
Subject: Title\r\n
text ...\r\n"

Answer 1

Try this, using teststring

library(stringr)
fullnames <- unique(c(str_extract_all(teststring, "[a-zA-Z]+,\\s[a-zA-Z]+", simplify=TRUE)))
splitnames <- unlist(strsplit(fullnames, ","))
ans <- data.frame(Last=splitnames[c(TRUE,FALSE)], First=splitnames[c(FALSE,TRUE)])

Output

   Last  First
1   Doe   John
2   Doe   Jane
3   Moe  James
4 Klein   John