#' fars_read function
#' read a csv file given a route to the file.
#'
#' @param filename an string indicating the complete route or relative route (from the working directory) to the file. The file can be compressed.
#'
#' @return a table_df that contents the data of csv. If the file doesn?t exist returns an error.
#'
#' @importFrom readr read_csv
#' @importFrom dplyr tbl_df
#'
#' @examples
#' \dontrun{
#' fars_read (accident_2013.csv.bz2)
#' fars_read (accident_2014.csv.bz2)
#' }
#'
#' @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)
}
#' make_filename function
#' given a year, makes the complete name of the "accident" filename. It has the form "accident_year.csv.bz2"
#' where year is substituted by /code{"year"}
#'
#' @param year an integer or string indicating the year to which we want to obtain the filename
#'
#' @return an string that represents the complete name of the filename.
#'
#' @examples
#' \dontrun{
#' make_filename(2013)
#' make_filename(2014)
#' }
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' fars_read_years fuction
#' given a list of years, extracts for each year the MONTH column
#' and a year column of the accident data of that year.
#' @param years a vector or list of integers representing the years
#' @return a list of dataframes of the same length of /code {"year"}.
#' Each element of the list refers to a year of the list and si a dataframe that
#' includes the MONTH column of the accident data of the year and a column with the year.
#' If there is no data of the year the element of the list will be null.
#'
#' @importFrom dplyr mutate
#' @importFrom dplyr select
#' @importFrom magrittr "%>%"
#'
#' @examples
#' \dontrun{
#' fars_read_years(c(2013, 2014))
#' }
#'
#' @export
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)
})
})
}
#' fars_summarize_years function
#' given a list of years gives the number of accidents by month of each of the years
#'
#' @param years a vector or list of ints or strings representing years
#'
#' @return a table which variables are the years on list and an unique
#' file that indicates the number of accidents by month of this year
#'
#' @examples
#' \dontrun{
#' fars_summarize_years(c(2013, 2014, 2015))
#'}
#'
#' @importFrom dplyr bind_rows
#' @importFrom dplyr group_by
#' @importFrom dplyr summarize
#' @importFrom tidyr spread
#' @importFrom dplyr n
#'
#' @export
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)
}
#' fars_map_state function
#'
#' given an state and a year plots the coordenates of the accidents in
#' this state an year
#'
#' @param state.num the number of the state for which we want
#' to draw the accident's coordinates.
#' @param year an integer indicating the year for which we want to draw the accident?s coordinates
#'
#' @return a plot with all accident's coordinates drawed of the /code{state.num}
#' and /code{year} or null if the /code{state.num} does not exist
#'
#' @importFrom dplyr filter
#' @importFrom maps map
#' @importFrom graphics points
#'
#' @examples
#'\dontrun{
#' fars_map_state(1,2013)
#'}
#' @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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