Function to pull data from FENIX API in FAOSTAT

readFAOData

library(httr)

readFAOData <- function(area_codes, element_codes, item_codes, year_codes, 
                        area_format = "M49",
                        item_format = "CPC",
                        dataset = "FBS", 
                        metadata_cols = c("codes", "units", "flags", "notes"),
                        include_na = FALSE,
                        return_n_records_only = FALSE,
                        base_url = "https://fenixservices.fao.org/faostat/api/v1/en/data/"){
  
  coll <- function(string){
    paste0(string, collapse = ",")
  }
  
  area_coll     = coll(area_codes)
  item_coll     = coll(item_codes)
  element_coll  = coll(element_codes)
  year_coll     = coll(year_codes)
  
  params <- list(
    area = area_coll, #These are FAO codes even if displayed in M49
    area_cs = area_format,
    element = element_coll,
    item = item_coll, #I think these are FAO codes too, but they _happen_ to match for CPC
    item_cs = item_format,
    year = year_coll,
    show_codes = "codes" %in% metadata_cols,
    show_unit = "units" %in% metadata_cols,
    show_flags = "flags" %in% metadata_cols,
    show_notes = "notes" %in% metadata_cols,
    null_values = include_na,
    no_records = return_n_records_only,  # Used to only return the number of records
    # page_number = 1,   # For pagination
    # page_size = 100,   # Number of records for pagination
    datasource = "DB4",
    output_type = "objects"
  )
  
  resp <- GET(paste0(base_url, dataset), query = params)
  
  if(status_code(resp) != 200){
    stop("Request failed")
  }
  
  resp_list <- content(resp)
  
  ret <- lapply(resp_list$data, as.data.frame)
  return(do.call(rbind, ret))
}