jst_get_total_pages: Calculate total pages
In jstor: Read Data from JSTOR/DfR

Description Usage Arguments Details Value Examples

This function is a simple helper to calculate the total number of pages of an article.

1	jst_get_total_pages(first_page, last_page, page_range, quietly = FALSE)

`first_page`	The first page of an article (numeric).
`last_page`	The last page of an article (numeric).
`page_range`	The page range of an article (character).
`quietly`	Sometimes page ranges contain roman numerals like `xiv`. These are not recognized, return `NA` and raise a warning. If set to `TRUE`, this warning not raised.

This function deals with four cases:

if all three arguments are missing, NA is returned.
if page_range is supplied, the number of pages is calculated from it.
if only the first page is supplied, NA is returned.
if first and last page are supplied, the number of pages is calculated as last_page - first_page + 1.

The algorithm to parse page ranges works as follows: A typical page range is 1-10, 200 where the article starts at page 1, ends at page 10, and has an erratum at page 200. For this case, the range is calculated as range + single_page, as in(10 - 1 + 1) + 1 = 11. Sometimes multiple ranges are given: 1-10, 11-20. For those cases all ranges are summed: (10 - 1 + 1) + (20 - 11 + 1) = 20. Another specification for multiple ranges is 1-10+11-20, which is treated similarly.

A vector with the calculated total pages.

# calculate pages from first and last page
first_pages <- sample(30:50, 10)
last_pages <- first_pages + sample(5:20, 10)
page_ranges <- rep(NA_character_, 10)

jst_get_total_pages(first_pages, last_pages, page_ranges)

# get pages from page range
jst_get_total_pages(NA_real_, NA_real_, "51 - 70")
jst_get_total_pages(NA_real_, NA_real_, "51 - 70, 350")
jst_get_total_pages(NA_real_, NA_real_, "350, 51 - 70")
jst_get_total_pages(NA_real_, NA_real_, "51 - 70, 80-100")
jst_get_total_pages(NA_real_, NA_real_, "51-70+350")