R/station_distance.R

In zyang2k/bluebike: Blue Bike Comprehensive Data

globalVariables(c(
  "station_data"
))
#' Compute the distance from stations given current location
#'
#' This function returns stations with distance in ascending order given the user's current location
#'
#' @importFrom dplyr mutate
#' @importFrom sf st_as_sf
#' @importFrom sf st_distance
#' @importFrom tidyselect starts_with
#' @importFrom magrittr "%>%"
#' @return a tbl_df object showing the distance between the user and top five closest stations with ID, name, number of docks, and position
#' @param long longtitude of user location
#' @param lat latitude of user location
#' @export station_distance
#' @examples
#' # Calculate distance for user at (-71.11467361, 42.34414899) and show the closest five stations
#' top_5_station <- head(station_distance(-71.11467361, 42.34414899), 5)
station_distance <- function(long, lat) {
  long <- as.numeric(long)
  lat <- as.numeric(lat)

  if (long < -180 | long > 180) {
    stop("please enter a valid longitude between -180 and 180")
  }
  if (lat < -90 | lat > 90) {
    stop("please enter a valid latitude between -90 and 90")
  }

  station_sf <- st_as_sf(station_data,
    coords = c("longitude", "latitude"),
    crs = 4326
  )

  user_sf <- c("longitude" = long, "latitude" = lat) %>%
    `t`() %>%
    as.data.frame() %>%
    st_as_sf(coords = c("longitude", "latitude"), crs = 4326)

  temp <- st_distance(x = station_sf, y = user_sf) %>%
    as.data.frame() %>%
    mutate(
      station_ID = station_data$number,
      station_name = station_data$name,
      station_position = station_sf$geometry,
      docks = station_data$total_docks
    ) %>%
    rename(distance = ".")

  ordered_station <- temp[order(temp$distance), ]
  return(ordered_station)
}