#' This function is created in order to check if the file exists and then make it as a data frame
#' and will throw an error if the file does not exist
#'
#' You can firstly check if the file exists the \code{stop} function
#'
#' @param filename input the name of the file as charater
#'
#' @return fars_read this function returns an input data with data frame format
#'
#' @examples
#' \dontrun{
#' data <- fars_read(file.csv)
#' }
#'
#' @importFrom readr read_csv
#' @importFrom dplyr tbl_df
#'
#' @export
fars_read <- function(filename) {
if(!file.exists(filename))
stop("file '", filename, "' does not exist")
data <- suppressMessages({
readr::read_csv(filename, progress = FALSE)
})
dplyr::tbl_df(data)
}
#' The function creates a filename for a .csv.bz2 file based on the \code{year}
#' argument in a form "accident_<year>.csv.bz2". It requires a numerical or
#' integer input otherwise ends with an error.
#'
#' @param year the input year as integer or string that when the file was generated
#'
#' @return make_filename this function returns a character vector of file name "accident_X.csv.bz2"
#' where X will be replaced by the year
#'
#' @examples
#' \dontrun{
#' make_filename(2015)
#' }
#'
#' @export
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' The function is to take a list of years and returns a list of data
#' frames with MONTH and year columns based on data in "accident_X.csv.bz2" files.
#' The files need to be in the working directory (Check function fars_read above!).
#'
#' @param years A list of years of integer or string that when the files were generated
#'
#' @return Returns a list of tibbles (data frames) with the same number of rows
#' as the data in "accident_<year>.csv.bz2" files and two columns - MONTH and
#' year. Returns NULL and a warning if the file does not exist.
#'
#' @examples
#' \dontrun{
#' fars_read_years(2013:2015)
#' fars_read_years(list(2013, 2014))
#' fars_read_years(2016) #example of warning (return error!)
#' }
#'
#' @inheritParams fars_read
#'
#' @importFrom dplyr mutate select %>%
#' @importFrom stats setNames
#'
#' @export
fars_read_years <- function(years) {
lapply(years, function(year) {
file <- make_filename(year)
tryCatch({
dat <- fars_read(file)
dplyr::mutate_(dat, .dots = setNames(list(~year)), year) %>%
dplyr::select_(~MONTH, ~year)
}, error = function(e) {
warning("invalid year: ", year)
return(NULL)
})
})
}
#' Counts number of accidents per month and year
#'
#' Based on the list of years, the function calculates the number of accidents
#' in the US on a monthly basis. The accident files need to be in the working
#' directory, the years can be passed as a list or a vector.
#'
#' @param years A list of years of integer or string that when the files were generated
#'
#' @return this function returns a data frame with total number of accidents for each month
#' which is converted to a wide format
#'
#' @examples
#' \dontrun{
#' fars_read_years(2013:2014)
#' fars_read_years(2016) #example of warning (return error!)
#' }
#'
#' @inheritParams fars_read_years
#'
#' @importFrom dplyr bind_rows group_by summarize %>%
#' @importFrom tidyr spread
#' @importFrom stats setNames
#'
#' @export
fars_summarize_years <- function(years) {
dat_list <- fars_read_years(years)
dplyr::bind_rows(dat_list) %>%
dplyr::group_by_(~year, ~MONTH) %>%
dplyr::summarize_(.dots = setNames(~n(), "n")) %>%
tidyr::spread_(~year, ~n)
}
#' The function is to take a number of a state in US and a year then filter the data, and
#' plot a map of all the accidents in that state. The input state number must be in the data! (correct state)
#' The files need to be in the working directory (Check function fars_read above!).
#'
#' @param state.num a number of a state in US as integer
#' @param year an input year as integer
#'
#' @return Returns a plot of the accidents based on the \code{state.num} and
#' \code{year} inputs. Returns an error if the state or year do not exist in the
#' data set.
#'
#' @examples
#' \dontrun{
#' fars_map_state(45, 2015)
#' fars_read_years(2016) #example of warning (return error!)
#' fars_read_years(60, 2016) #example of warning (return error!)
#' }
#'
#' @importFrom dplyr filter
#' @importFrom maps map
#' @importFrom graphics points
#'
#' @export
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)
})
}
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