R/ecb-euro-rates.R

In bbk: Client for Central Bank APIs

#' Euro foreign exchange reference rates
#'
#' Fetch the latest or historical Euro foreign exchange reference rates from
#' the European Central Bank.
#'
#' @details
#' Note you can achieve the same by calling the [ecb_data()] function with the right
#' parameters for each currency.
#'
#' The reference rates are usually updated at around 16:00 CET every working day,
#' except on [TARGET closing days](https://www.ecb.europa.eu/ecb/contacts/working-hours/html/index.en.html).
#'
#' They are based on the daily concertation procedure between central banks across
#' Europe, which normally takes place around 14:10 CET. The reference rates are
#' published for information purposes only.
#' Using the rates for transaction purposes is strongly discouraged.
#'
#' @param x (`character(1)`) one of "latest" or "history". Default "latest".
#' @returns A [data.table::data.table()] with the reference rates.
#'
#' @source <https://www.ecb.europa.eu/stats/policy_and_exchange_rates/euro_reference_exchange_rates/html/index.en.html>
#' @export
#' @examplesIf curl::has_internet()
#' \donttest{
#' ecb_euro_rates()
#' }
ecb_euro_rates <- function(x = c("latest", "history")) {
  x <- match.arg(x)
  url <- switch(x,
    latest = "https://www.ecb.europa.eu/stats/eurofxref/eurofxref.zip",
    history = "https://www.ecb.europa.eu/stats/eurofxref/eurofxref-hist.zip"
  )
  tmp <- tempfile()
  dir.create(tmp)
  on.exit(unlink(tmp, recursive = TRUE), add = TRUE)
  tf <- file.path(tmp, "tempfile.zip")
  curl::curl_download(url, tf)
  file <- utils::unzip(tf, exdir = tmp)
  dt <- fread(tf, sep = ",")
  fmt <- if (nrow(dt) > 1L) "%Y-%m-%d" else "%d %B %Y"
  dt[, Date := as.Date(Date, format = fmt)]
  dt[,
    names(.SD) := lapply(.SD, \(x) ifelse(x == "N/A", NA_real_, x)),
    .SDcols = is.character
  ]
  dt[, names(.SD) := lapply(.SD, as.numeric), .SDcols = !"Date"]
  dt <- melt(dt,
    id.vars = "Date",
    variable.name = "currency",
    value.name = "rate",
    variable.factor = FALSE
  )
  dt <- na.omit(dt)
  setnames(dt, tolower)
  dt
}