Harvest a repository using Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) requests.
oaih_harvest(baseurl, prefix = "oai_dc",
             from = NULL, until = NULL, set = NULL,
             transform = TRUE)If the OAI-PMH request was successful, the result of the request as XML or (default) transformed to “useful” R data structures.
a character string giving the base URL of the repository.
a character vector with the formats in which metadata
    should be obtained, or NULL, indicating all available
    formats.  The default ("oai_dc") corresponds to the mandatory
    OAI unqualified Dublin Core metadata schema.
character strings or Date or
    POSIXt date/time objects giving
    datestamps to be used as lower or upper bounds, respectively, for
    datestamp-based selective harvesting (i.e., only harvest records
    with datestamps in the given range).  If character, dates and times
    must be encoded using ISO 8601 in either %F or
    %FT%TZ format (see strptime).  The trailing
    Z must be used when including time.  OAI-PMH implies
    UTC for data/time specifications.
a character vector giving the sets to be used for selective
    harvesting (i.e., only harvest records in the given sets), or
    NULL.
a logical indicating whether the OAI-PMH XML results
    to “useful” R data structures via oaih_transform.
    Default: true.
This is a high-level function for conveniently harvesting metadata from a repository, allowing specifying several metadata formats or sets. It also maps datestamps specified as R date or date/time objects to valid OAI-PMH datestamps according to the granularity of the repository.