Get ULAN prefName for a given ID from the Getty Vocabularies SPARQL endpoint

prefName.r

library(tidyverse)
library(httr)

get_prefname <- function(id) {
  message(id)
  endpoint <- "http://vocab.getty.edu/sparql.csv?query="
  query <- URLencode(str_interp("SELECT ?prefName WHERE {
      ?person dc:identifier '${id}';
      xl:prefLabel [xl:literalForm ?prefName ] .
    } LIMIT 1"))
  
  try_ulan <- possibly(function(ep, qu) {
    read_csv(str_interp("${ep}${qu}"), col_types = "c")
    }, otherwise = data.frame())
  
  
  Sys.sleep(0.3)
  res <- try_ulan(endpoint, query)
  if (nrow(res) == 1) {
    return(res[[1,1]])
  } else {
    return(NA_character_)
  }
}