This question is a follow-up of this.
The following metadata.txt has been generated by:
pdftk sample.pdf dump_data > metadata.txt
metadata.txt:
InfoBegin
InfoKey: ModDate
InfoValue: D:20170817080316Z00'00'
InfoBegin
InfoKey: CreationDate
InfoValue: D:20170817080316Z00'00'
InfoBegin
InfoKey: Creator
InfoValue: Adobe Acrobat 7.0
InfoBegin
InfoKey: Producer
InfoValue: Mac OS X 10.9.5 Quartz PDFContext
PdfID0: 76cf9fd41f0778314abfec8b34d8388d
PdfID1: 76cf9fd41f0778314abfec8b34d8388d
NumberOfPages: 612
BookmarkBegin
BookmarkTitle: Contents
BookmarkLevel: 1
BookmarkPageNumber: 11
BookmarkBegin
BookmarkTitle: Preface
BookmarkLevel: 1
BookmarkPageNumber: 5
BookmarkBegin
BookmarkTitle: Explanatory Note and Abbreviations Used
BookmarkLevel: 1
BookmarkPageNumber: 7
PageMediaBegin
PageMediaNumber: 1
PageMediaRotation: 0
PageMediaRect: 0 0 405 616
PageMediaDimensions: 405 616
I would like R to read the Table-of-Contents (TOC) information from metadata.txt into a data.frame, starting from the first BookmarkBegin to the BookmarkPageNumber immediately before PageMediaBegin.
The area of interest can be filtered out with the following code:
require(stringi)
connect=file('metadata.txt')
metadata=readLines(connect)
existing_toc=c(min(grep('BookmarkBegin', metadata)),max(grep('BookmarkPageNumber', metadata)))
metadata_toc=metadata[existing_toc[1]:existing_toc[2]]
Removing BookmarkBegin and splitting the strings on each line by every first occurrence of : via:
toc_data=metadata_toc[-grep('BookmarkBegin', metadata_toc)]
toc_data_split=stri_split_fixed(toc_data, ": ", n=2)
lands me with the following list:
[[1]]
[1] "BookmarkTitle" "Contents"
[[2]]
[1] "BookmarkLevel" "1"
[[3]]
[1] "BookmarkPageNumber" "11"
[[4]]
[1] "BookmarkTitle" "Preface "
[[5]]
[1] "BookmarkLevel" "1"
[[6]]
[1] "BookmarkPageNumber" "5"
[[7]]
[1] "BookmarkTitle"
[2] "Explanatory Note and Abbreviations Used "
[[8]]
[1] "BookmarkLevel" "1"
[[9]]
[1] "BookmarkPageNumber" "7"
How should I continue from here to get a data.frame like so:
structure(list(BookmarkTitle = structure(c(1L, 3L, 2L), .Label = c("Contents",
"Explanatory Note and Abbreviations Used", "Preface"), class = "factor"),
BookmarkLevel = c(1, 1, 1), BookMarkPageNumber = c(11, 5,
7)), .Names = c("BookmarkTitle", "BookmarkLevel", "BookMarkPageNumber"
), row.names = c(NA, -3L), class = "data.frame")
BookmarkTitle BookmarkLevel
1 Contents 1
2 Preface 1
3 Explanatory Note and Abbreviations Used 1
BookMarkPageNumber
1 11
2 5
3 7
This base solution will convert metadata_toc to a data frame. First replace each line not having a colon with an empty line. It is now in Debian Control File (DCF) format so read it using read.dcf. Convert the resulting matrix m to a data frame DF and convert the column types to character and numeric.
metadata_toc[grep(":", metadata_toc, invert = TRUE)] <- ""
m <- read.dcf(textConnection(metadata_toc))
DF <- as.data.frame(m, stringsAsFactors = FALSE)
DF[] <- lapply(DF, type.convert, as.is = TRUE)
giving:
> DF
BookmarkTitle BookmarkLevel BookmarkPageNumber
1 Contents 1 11
2 Preface 1 5
3 Explanatory Note and Abbreviations Used 1 7
metadata_toc <- c("BookmarkBegin", "BookmarkTitle: Contents", "BookmarkLevel: 1",
"BookmarkPageNumber: 11", "BookmarkBegin", "BookmarkTitle: Preface ",
"BookmarkLevel: 1", "BookmarkPageNumber: 5", "BookmarkBegin",
"BookmarkTitle: Explanatory Note and Abbreviations Used ", "BookmarkLevel: 1",
"BookmarkPageNumber: 7")