getRversion() >= "3.1.0"
utils::suppressForeignCheck(c("STATE", "MONTH", "year"))
globalVariables(c("STATE", "MONTH", "year"), package = "fars", add = FALSE)
#' Read csv file into data frame tbl
#'
#' This is a simple function that reads a csv file and returns a data frame tbl (or tibble)
#'
#' @param filename the name of the file which the data are to be read from.
#'
#' @return This function returns a data frame tbl (a tibble).
#'
#'
#' @note This function returns an error if the filename does not exist.
#'
#' @importFrom readr read_csv
#' @import dplyr
#' @import magrittr
#'
#' @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)
}
#' Create filenames
#'
#' This is a simple function that creates filenames matching the naming conventions for using US National Highway Traffic Safety Administration's Fatality Analysis Reporting System data.
#'
#' @param year the year to be read in 4 digits such as e.g 2013 or 2014.
#'
#' @return This function returns a character string describing a filename.
#'
#' @examples
#' make_filename(2013)
#'
#' @export
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' Read month and year information for selected years
#'
#' This is a simple function that reads month and year information for each available entry.
#'
#' @param years a vector of 4 digits years.
#'
#' @return This function returns a list containing Month and year for each table entry.
#'
#' @examples
#' fars_read_years(c(2013:2015))
#'
#' @note This function returns an error if the year argument does not exist in the available data sets.
#'
#' @import dplyr
#' @import magrittr
#'
#' @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)
})
})
}
#' Summarize monthly accidents per year
#'
#' This is a simple function that creates a wide table containing the monthly number of accidents for a given vector of years.
#'
#' @param years a vector of 4 digits years.
#'
#' @return This function returns a tibble with 12 rows for each month and the selected years as variables.
#'
#'
#' @note This function returns an error if the selected year argument does not exist in the available data sets.
#'
#' @import dplyr
#' @import magrittr
#' @importFrom tidyr spread
#'
#' @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)
}
#' Draw a map of accidents
#'
#' This function draws a map of accidents for a given year in a specific state.
#'
#' @param state.num numerical state indicator
#' @param year a 4 digits year argument
#'
#' @return This function returns a map showing the car accidents for a given year for a specific state.
#'
#'
#' @note This function returns an error if the selected year argument does not exist in the available data sets and gives a message if no accidents to plot.
#'
#' @import dplyr
#' @import magrittr
#' @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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