R/get_pollution_history.R

In UBC-MDS/rpollution: Visualises future, historic and current air pollution data

#' Returns a dataframe of pollution history for a location between
#' a specified date range.
#'
#' Given a specified date range, the function makes an API request
#' to the OpenWeather Air Pollution API and fetches historic
#' pollution data for a given location.
#'
#' Note: Historical data is accessible from 27th November 2020
#'
#' @param start_date The start date as a UNIX timestamp, e.g. 1606488670
#' @param end_date The end date as a UNIX timestamp, e.g. 1606747870
#' @param lat Latitude coordinate for a given location as a double
#' @param lon Longitude coordinate for a given location as a double
#' @param api_key The API key for OpenWeather as a string
#'
#' @return data frame containing pollution history
#' @export
#'
#' @examples
#' get_pollution_history(1606488670, 1606747870, 49.28, 123.12, "APIKEY_example")
get_pollution_history <- function(start_date, end_date, lat, lon, api_key) {
  if (!is.numeric(start_date)) {
    stop("start_date input should be an int")
  }

  if (!is.numeric(end_date) | end_date != round(end_date)) {
    stop("end_date input should be an int")
  }

  if (!is.numeric(lat)) {
    stop("latitude input should be a float or an integer")
  }

  if (!is.numeric(lon)) {
    stop("longitude input should be a float or an integer")
  }


  api_url <- "http://api.openweathermap.org/data/2.5/air_pollution/history?"

  query <- list(
    lat = lat,
    lon = lon,
    start = start_date,
    end = end_date,
    appid = api_key
  )

  tryCatch(
    {
      res <- httr::GET(api_url, query = query)

      # Stop if response status is not 200
      httr::stop_for_status(res)

      data <- jsonlite::fromJSON(httr::content(res, as = "text", encoding = "UTF-8"),
        flatten = TRUE
      )

      data$list
    },
    error = function(e) {
      "An error occurred fetching data from the API"
    }
  )
}