Convenience functions for https://openexchangerates.org/

exchange-rates.R

# (1) Get a free plan from https://openexchangerates.org/signup/free
# (2) Tell this function your API key -- Sys.setenv("OER_KEY", "your-key-here")
getDay <- function(day) {
  u <- sprintf(
    "https://openexchangerates.org/api/historical/%s.json?app_id=%s",
    day, Sys.getenv("OER_KEY")
  )
  res <- jsonlite::fromJSON(u)
  # convert timestamp to date object
  # http://stackoverflow.com/questions/13456241/convert-unix-epoch-to-date-object-in-r
  res$rates$date <- as.POSIXct(res$timestamp, origin = "1970-01-01")
  data.frame(res$rates)
}

getRates <- function(start = end - 3, end = Sys.Date()) {
  days <- seq(start, end, by = "1 day")
  Reduce("rbind", lapply(days, getDay))
}

dat <- getRates()
dat[, c("AUD", "NZD", "date")]

#>        AUD      NZD                date
#> 1 1.403416 1.528405 2015-11-13 10:00:00
#> 2 1.402924 1.529136 2015-11-14 10:00:00
#> 3 1.402924 1.529136 2015-11-15 10:00:00
#> 4 1.402924 1.529136 2015-11-15 12:00:11