R/weather_data.R

In shihs/LiUAdRLab5: City forecast

#' City forecast
#'
#' forecast_data function will get FIVE days temperature forecast data from OpenWeatherMap API(\url{https://openweathermap.org}).
#'
#' @param city character, a city name
#' @param time character, default is 'day_average'
#'
#'  day_average: Get average temperature in each day
#'
#'  hours: Get temperature of every 3 hours
#'
#' @return a data.frame, five days temperature forecast of the city
#'
#' @examples
#' forecast_data("stockholm")
#'
#' @export
forecast_data <- function(city, time = "day_average") {

  d <- .get_weather_data(city)

  # temperature data
  df <- d$list
  # tranfer temperature from Kelvins to Celsius
  temp <- df$main$temp - 273.15

  # country
  country <- rep(d$city$country, nrow(df))

  if (time == "day_average") {
    # date
    date <- substr(df$dt_txt, 1, 10)

    df <- data.frame(date = date, temp = temp, country = country)

    # get average for everyday
    df <- df %>%
      dplyr::select(date, temp, country) %>%
      dplyr::group_by(date, country) %>%
      dplyr::summarize(mean_temp = mean(temp))
    df <- data.frame(df)
  }

  if (time == "hours") {
    # country <- rep(d$city$country, nrow(df))
    date <- substr(df$dt_txt, 1, 16)
    df <- data.frame(date = date, temp = temp, country = country)
  }

  return (df)

}





.get_weather_data <- function(city) {
  # key for the api
  key <- "3c656bd3014279a8f41b90522c014977"
  url <- paste0("https://api.openweathermap.org/data/2.5/forecast?q=", city, "&appid=", key)

  if (httr::status_code(httr::GET(url)) == 404) {
    stop("city not found!")
  }

  d <- jsonlite::fromJSON(url)

  return (d)

}



#' @importFrom magrittr %>%
#' @importFrom jsonlite fromJSON
#' @importFrom httr GET
#' @importFrom httr status_code
#' @import dplyr
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