R/fars_functions.R

In dfrail24/pkg: Imports & visualizes FARS data

#' FARS data import
#'
#' Reads in FARS data
#' @param filename File (CSV) name
#' @return Data frame table
#' @export
#' @examples \dontrun{
#' fars_read("accident_2013.csv")
#' }
#'

fars_read <- function(filename) {
  if(!file.exists(system.file("extdata", filename, package = "pkg")))
    stop("file '", filename, "' does not exist")
  data <- suppressMessages({
    # readr::read_csv(filename, progress = FALSE)
    readr::read_csv(system.file("extdata", filename, package = "pkg"))
  })
  dplyr::tbl_df(data)
}


#'Create filename
#'
#'Create filename for FARS data
#'@param year Year that data were collected
#'@return Filename
#'@export
#'@examples \dontrun{
#'make_filename(2017)
#'}
#'

make_filename <- function(year) {
  year <- as.integer(year)
  sprintf("accident_%d.csv.bz2", year)
}


#' Read Multiple Files
#'
#' Read multiple files and confirm that the years are valid
#' @param years Years that data were collected
#' @return List of data frames (NULL if data do not exist)
#' @export
#' @examples \dontrun{
#' fars_read_years(2013:2015)
#' }
#'

fars_read_years <- function(years) {
  lapply(years, function(year) {
    file <- make_filename(year)
    tryCatch({
      dat <- fars_read(file)
      dplyr::mutate(dat, year = year) %>%
        dplyr::select(MONTH, year)
    }, error = function(e) {
      warning("invalid year: ", year)
      return(NULL)
    })
  })
}

#' Summarize data
#'
#' Summarize yearly data by month
#' @param years Years that data were collected
#' @return Summary
#' @export
#' @examples \dontrun{
#' fars_summarize_years(2013:2015)
#' }
#'

fars_summarize_years <- function(years) {
  dat_list <- fars_read_years(years)
  dplyr::bind_rows(dat_list) %>%
    dplyr::group_by(year, MONTH) %>%
    dplyr::summarize(n = n()) %>%
    tidyr::spread(year, n)
}


#' Create map
#'
#' Create map visualization of FARS data
#' @param state.num State number
#' @param year Year that data were collected
#' @return Visual map
#' @export
#' @examples \dontrun{
#' fars_map_state(1, 2013)
#' }

fars_map_state <- function(state.num, year) {
  filename <- make_filename(year)
  data <- fars_read(filename)
  state.num <- as.integer(state.num)

  if(!(state.num %in% unique(data$STATE)))
    stop("invalid STATE number: ", state.num)
  data.sub <- dplyr::filter(data, STATE == state.num)
  if(nrow(data.sub) == 0L) {
    message("no accidents to plot")
    return(invisible(NULL))
  }
  is.na(data.sub$LONGITUD) <- data.sub$LONGITUD > 900
  is.na(data.sub$LATITUDE) <- data.sub$LATITUDE > 90
  with(data.sub, {
    maps::map("state", ylim = range(LATITUDE, na.rm = TRUE),
              xlim = range(LONGITUD, na.rm = TRUE))
    graphics::points(LONGITUD, LATITUDE, pch = 46)
  })
}