R/dpla_fields.r

In ropensci/rmetadata: Work with many Scholarly Metadata APIs in R.

#' Search metadata from the Digital Public Library of America (DPLA).
#'
#' @import httr jsonlite stringr
#' @export
#' @param queries A list of query terms paired with the fields you want to
#'    search them in. You can search on specific fields, see details below.
#' @details You can search on a vector of the fields to return in the output.
#'    The default is all fields. Options are:
#'    \itemize{
#'      \item title - Object title
#'      \item description - Description
#'      \item subject - Subjects, semicolon separated
#'      \item language - Language
#'      \item format - Format, one of X, Y.
#'      \item collection - Collection name
#'      \item type - Type of object
#'      \item publisher - Publisher name
#'      \item creator - Creator
#'      \item provider - Data provider
#'      \item score - Matching score on your query
#'      \item creator - Creator
#'    }
#' @return A list for now...
#' @examples \dontrun{
#' # Search by specific fields
#' dpla_by_fields(queries=c("fruit,title","basket,description"))
#'
#' # Items from before 1900
#' dpla_by_fields("1900,date.before")
#'
#' dpla_by_fields("Boston,spatial")
#' }

dpla_by_fields <- function(queries = NULL)
{
  url = "http://api.dp.la/v2/items"
  key <- getOption("dplakey")

  args <- list()
  for(i in seq_along(queries)){
    assign(paste("sourceResource", str_split(queries[[i]], ",")[[1]][[2]], sep="."), str_split(queries[[i]], ",")[[1]][[1]])
    args[[list(grep("sourceResource", ls(), value=TRUE))[[1]][[i]]]] <- eval(parse(text=grep("sourceResource", ls(), value=TRUE)[[i]]))
  }

  args <- rmet_compact(c(args, api_key=key))
  tt <- GET(url, query = args)
  warn_for_status(tt)
  assert_that(tt$headers$`content-type` == "application/json; charset=utf-8")
  res <- content(tt, as = "text")
  jsonlite::fromJSON(res, FALSE)
}