Example HTTP GET request for accessing the PTV API in R

ptv_get.R

# This function formulates and submits a HTTP GET request to the Public
# Transport Victoria (PTV) API. In particular, it calculates the "signature"
# component of the URL required for authentication. While I've included the
# version number as an argument, I haven't tested this function on versions
# other than 3.
#
# See URL below for information on obtaining a user ID (also called a devid) and
# an API key:
# https://www.ptv.vic.gov.au/footer/data-and-reporting/datasets/ptv-timetable-api/
#
# Example usage: ptv_get("routes", user_id, api_key)
# Required libraries: httr, digest, glue

ptv_get <- function(request, user_id, api_key, version = 3) {
  base_url <- "http://timetableapi.ptv.vic.gov.au"
  signature <- digest::hmac(
    key = api_key,
    object = glue::glue("/v{version}/{request}?devid={user_id}"),
    algo = "sha1"
  )
  complete_url <- glue::glue(
    base_url,
    "/v{version}",
    "/{request}",
    "?devid={user_id}",
    "&signature={toupper(signature)}"
  )
  httr::GET(url = complete_url)
}