R/spq_head.R

In lvaudor/glitter: glitter makes SPARQL

#' Return the first lines of results
#' @param .query a list with elements of the query
#' @param n the maximum number of lines to return
#' @return A query object
#' @export
#' @examples
#' # Return the default of 5 items
#' spq_init() %>%
#' spq_add("?item wdt:P31 wd:Q5") %>%
#' spq_label(item) %>%
#' spq_add("?item wdt:P19/wdt:P131* wd:Q60") %>%
#' spq_add("?item wikibase:sitelinks ?linkcount") %>%
#' spq_arrange(desc(linkcount)) %>%
#' spq_head()
#'
#' # Return 42 items
#' spq_init() %>%
#' spq_add("?item wdt:P31 wd:Q5") %>%
#' spq_label(item) %>%
#' spq_add("?item wdt:P19/wdt:P131* wd:Q60") %>%
#' spq_add("?item wikibase:sitelinks ?linkcount") %>%
#' spq_arrange(desc(linkcount)) %>%
#' spq_head(42)
#' @inheritSection spq_offset Subsetting
spq_head = function(.query, n = 5) {

  if (is.null(n)) return(.query)

  .query[["limit"]] = n
  .query
}