Split and recombine EPUB text sections based on regular expression pattern matching.
Arguments
- data
a data frame created by
epub.- pattern
character, a regular expression.
- sift
NULLor a named list of parameters passed toepub_sift. See details.
Details
This function takes a regular expression and uses it to determine new break points for the full e-book text.
This is particularly useful when sections pulled from EPUB metadata have arbitrary breaks and the text contains meaningful breaks at random locations in various sections.
epub_recombine collapses the text and then creates a new nested data frame containing new chapter/section labels, word counts and character counts,
associated with the text based on the new break points.
Usefulness depends on the quality of the e-book. While this function exists to improve the data structure of e-book content parsed from e-books with poor metadata formatting, it still requires original formatting that will at least allow such an operation to be successful, specifically a consistent, non-ambiguous regular expression pattern. See examples below using the built in e-book dataset.
When used in conjunction with epub_sift via the sift argument, recombining and resifting is done recursively.
This is because it is possible that sifting can create a need to rerun the recombine step in order to regenerate proper chapter indexing for the section column.
However, recombining a second time does not lead to a need to resift, so recursion ends after one round regardless.
This is a convenient way to avoid the syntax:
epub_recombine([args]) %>% epub_sift([args]) %>% epub_recombine([args]).
Examples
# \donttest{
file <- system.file("dracula.epub", package = "epubr")
x <- epub(file) # parse entire e-book
x$data[[1]] # note arbitrary section breaks (not between chapters)
#> # A tibble: 15 × 4
#> section text nword nchar
#> <chr> <chr> <int> <int>
#> 1 item6 "The Project Gutenberg EBook of Dracula, by Br… 11446 60972
#> 2 item7 "But I am not in heart to describe beauty, for… 13879 71798
#> 3 item8 "\" 'Lucy, you are an honest-hearted girl, I k… 12474 65522
#> 4 item9 "CHAPTER VIIIMINA MURRAY'S JOURNAL\nSame day, … 12177 62724
#> 5 item10 "CHAPTER X\nLetter, Dr. Seward to Hon. Arthur … 12806 66678
#> 6 item11 "Once again we went through that ghastly opera… 12103 62949
#> 7 item12 "CHAPTER XIVMINA HARKER'S JOURNAL\n23 Septembe… 12214 62234
#> 8 item13 "CHAPTER XVIDR. SEWARD'S DIARY-continued\nIT w… 13990 72903
#> 9 item14 "\"Thus when we find the habitation of this ma… 13356 69779
#> 10 item15 "\"I see,\" I said. \"You want big things that… 12866 66921
#> 11 item16 "CHAPTER XXIIIDR. SEWARD'S DIARY\n3 October.-T… 11928 61550
#> 12 item17 "CHAPTER XXVDR. SEWARD'S DIARY\n11 October, Ev… 13119 68564
#> 13 item18 " \nLater.-Dr. Van Helsing has returned. He ha… 8435 43464
#> 14 item19 "End of the Project Gutenberg EBook of Dracula… 2665 18541
#> 15 coverpage-wrapper "" 0 0
pat <- "CHAPTER [IVX]+" # but a reliable pattern exists for new breaks
epub_recombine(x, pat) # not as expected; pattern also in table of contents
#> # A tibble: 1 × 10
#> rights identifier creator title language subject date source nchap data
#> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <int> <list>
#> 1 Public … http://ww… Bram S… Drac… en Horror… 1995… http:… 54 <tibble>
epub_recombine(x, pat, sift = list(n = 1000)) # sift low word-count sections
#> # A tibble: 1 × 10
#> rights identifier creator title language subject date source nchap data
#> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <int> <list>
#> 1 Public … http://ww… Bram S… Drac… en Horror… 1995… http:… 27 <tibble>
# }