#' Reads FARS (Fatality Analysis Reporting System) data from cvs file.
#'
#' @export
#' @import readr
#' @import dplyr
#'
#' @param filename A string. Path to cvs data file.
#'
#' @section Warning:
#' Function will stop if provided file not found
#'
#' @return Loaded FARS data as \code{\link[dplyr]{tbl_df}}
#'
#' @examples
#' \dontrun{fars_read("accident_2014.csv.bz2")}
fars_read <- function(filename) {
if(!file.exists(filename))
stop("file '", filename, "' does not exist")
data <- suppressMessages({
readr::read_csv(filename, progress = FALSE, quote = "")
})
dplyr::tbl_df(data)
}
#' Genarates archive file name based on year value
#'
#' @export
#'
#' @param year A number.
#'
#' @return generated archive file as string
#'
#' @examples
#' \dontrun{make_filename("2011")}
#' \dontrun{make_filename(2011)}
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' Read FARS (Fatality Analysis Reporting System) data for years
#'
#' @export
#' @import dplyr
#'
#' @param years A vector of years values (numbers)
#'
#' @section Warning:
#' Function will skip year if file with data for year does not exists
#'
#' @return readed FARS data as \code{\link[dplyr]{tbl_df}}
#'
#' @examples
#' \dontrun{fars_read_years(c(2013:2015))}
#' \dontrun{fars_read_years(c(2013,2015))}
fars_read_years <- function(years) {
lapply(years, function(year) {
MONTH <- NULL
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 accidents from FARS data by year and month
#'
#' @export
#' @import dplyr
#'
#' @param years A vector of years values (numbers) to summarize
#'
#' @section Warning:
#' Function will skip year if file with data for year does not exists
#'
#' @return Summarized informaion about accidents as \code{\link[dplyr]{tbl_df}}.
#'
#' @examples
#' \dontrun{fars_summarize_years(c(2001:2011))}
#' \dontrun{fars_summarize_years(c("2004, 2008"))}
fars_summarize_years <- function(years) {
year <- NULL
MONTH <- NULL
dat_list <- fars_read_years(years)
dplyr::bind_rows(dat_list) %>%
dplyr::group_by(year, MONTH) %>%
dplyr::summarize(n = n()) %>%
tidyr::spread(year, n)
}
#' Display accidents state locations by year
#'
#' @export
#' @import dplyr
#' @import graphics
#' @import maps
#'
#' @param state.num US state index (string)
#' @param year A year value (number)
#'
#' @section Warning:
#' Function will skip year if file with data for year does not exists
#'
#' Function will stop if invalid state provided
#'
#' @return this function returns a US state map with dots representing the
#' fatalities in a given year for a FARS file
#'
fars_map_state <- function(state.num, year) {
STATE <- MONTH <- NULL
LATITUDE <- LONGITUD <- NULL
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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