#' Loads a CSV file to a tibble
#'
#' @description
#' This function loads a CSV file defined by \code{filename} argument to a tibble.
#' If the path is incorrect (file not existed), an error will be thrown.
#'
#' @param filename Path to the CSV file.
#'
#' @return a tibble result from loading file.
#'
#' @examples
#' \dontrun{
#' accident_2015 <- fars_read("accident_2015.csv.bz2")
#' }
#'
#' @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)
}
#' Make filename
#'
#' @description
#' This function creates a filename for a .csv.bz2 file based on the \code{year}
#' argument in a form "accident_<year>.csv.bz2". Function will end with an error
#' if input is not a an integer value.
#'
#' @param year Integer value indicating a year of a data set.
#'
#' @return string in a format "accident_<year>.csv.bz2"
#'
#' @examples
#' \dontrun{
#' makefilename(2017)
#' }
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' Reads month and year from accident files
#'
#' @description
#' This function returns a list of data frames with MONTH and year columns
#' based on data in "accident_<year>.csv.bz2 files.
#' The files need to be located in the working directory.
#'
#' @param years A vector or list of years in numeric or integer format.
#'
#' @return a list of tibbles with the same number of rows as the data in
#' "accident_<year>.csv.bz2" files and two columns - MONTH and
#' year. NULL value if year is invalid (also a warning will be raised).
#'
#' @examples
#' \dontrun{
#' fars_read_years(2013:2014)
#' fars_read_years(list(2013, 2014))
#'
#' # Results in a warning
#' fars_read_years(2016)
#' }
#'
#' @importFrom dplyr %>% mutate select
#'
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)
})
})
}
#' Counts number of accidents per month and year
#'
#' @description
#' 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 vector or list of years (numeric or integer) that will be
#' searched in the data
#'
#' @return a tibble with months in rows and selected years in columns containing
#' the number of accidents.
#'
#' @examples
#' \dontrun{
#' fars_summarize_years(2014:2015)
#' }
#'
#' @importFrom dplyr %>% bind_rows group_by summarize
#' @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")
}
#' Plots the accidents on a US state map
#'
#' @description
#' This function plots the accidents in a simple map. The state number should be
#' integer or numerical and should exist in the FARS data, otherwise the
#' function terminates with an error. Also returns an error if the data file for
#' the year input does not exist.
#'
#' @param state.num The number of a state in the US as used in the FARS data
#' sets. Must be integer
#' @param year The year of analysis. Must be integer.
#'
#' @return a plot of the accidents based on the \code{state.num} and
#' \code{year} inputs.
#'
#' @examples
#' \dontrun{
#' fars_map_state(45, 2015)
#'
#' # Results in an error
#' fars_map_state(45, 2016)
#' fars_map_state(60, 2015)
#' }
#'
#' @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)
})
}
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.