This API client for the Internet Archive is intended primarily
for searching for items, retrieving metadata for items, and downloading
the files associated with the items. The functions can be used with the
pipe operator (%>%
) from magrittr and the data
manipulation verbs in dplyr to create pipelines
from searching to downloading. For the full details of what is possible
with the Internet Archive API, see their advanced search
help.
First load the package. We will also use dplyr for manipulating the retrieved data.
The simplest way to search the Internet Archive is to use a keyword search. The following function searches for these keywords in the most important metadata fields, and returns a list of item identifiers.
## Warning in ia_keyword_search("isaac hecker"): Bad Request (HTTP 400).
## total items found. This query requested 5 results.
## NULL
You can pass an item identifier to the ia_browse()
function to open an item in your browser. If you pass this function
multiple identifiers, it will open only the first one.
Usually it is more useful to perform an advanced search. You can
construct an advanced search as a named character vector, where the
names correspond to the fields. The following search, for instance,
looks for items published by the American Tract Society in 1864. Run the
function ia_list_fields()
to see the list of accepted
metadata fields.
ats_query <- c("publisher" = "american tract society", "year" = "1864")
ia_search(ats_query, num_results = 3)
## Warning in ia_search(ats_query, num_results = 3): Bad Request (HTTP 400).
## total items found. This query requested 3 results.
## NULL
You can change the number of items returned by the search using the
num_results =
argument, and you can request subsequent
pages of results with the page =
argument.
Notice that ia_search()
and
ia_keyword_search()
both return a character vector of
identifiers, so both can be used in the same way at the beginning of a
pipeline.
To search by a date range, use the date
field and the
years (or ISO 8601
dates) separated by TO
. Here we search for publications
by the American Tract Society in the 1840s.
Once you have retrieved a list of items, you can retrieve their metadata and the list of files associated with the items.
To get a single item’s metadata, you can pass its identifier to the
ia_get_items()
function.
The result is a list where the names of items in the list are the
item identifiers, and the rest of the list is the metadata. This nested
list can be difficult to work with, so the ia_metadata()
returns a data frame of the metadata, and ia_files()
returns a data frame of the files associated with the item.
These functions can also retrieve the information for multiple items when used in a pipeline. Here we search for all the items about Hecker, retrieve their metadata, and turn it into a data frame. We then filter the data frame to get only the titles.
The ia_download()
function will download all the files
in a data frame returned from ia_files()
. This function
should be used with caution, and you should first filter the data frame
to download only the files that you wish. In the following example, we
retrieve a list of all the files associated with items published by the
American Tract Society in 1864. Then we filter the list so we get only
text files, then we pick only the first text file associated with each
item. Finally we download the files to a directory we specify (in this
case, a temporary directory).
dir <- tempdir()
ia_search(ats_query, num_results = 2) %>%
ia_get_items() %>%
ia_files() %>%
filter(type == "txt") %>%
group_by(id) %>%
slice(1) %>%
ia_download(dir = dir, overwrite = FALSE) %>%
glimpse()
Notice that ia_download()
returns a modified version of
the data frame that was passed to it, adding a column
local_file
with the path to the download files.
If the overwrite =
argument is FALSE
, then
you can pass the same data frame of files to ia_download()
and it will download only the files that it has not already
downloaded.