#' Read FARS file
#'
#' This function checks if the file exists in the work directory.
#' If does, it load it to a data frame.
#'
#' @param filename The file name that has the data that should be loaded.
#'
#' @return This functions returns a data frame with file data loaded, if it exists.
#' If the file doesn't exist, it stops the function and return a message telling that the file doesn't exist.
#'
#' @details This function uses read_csv function from readr package.
#' In order to load the file, it should be in the working directory.
#'
#' @examples
#' \dontrun{
#' fars_read("data/accident_2013.csv.bz2")
#' }
#'
#' @export
fars_read <- function(filename) {
full_path <- paste0(system.file("extdata", package = "fars"), "/", filename)
if(!file.exists(full_path))
stop("file '", filename, "' does not exist")
data <- suppressMessages({
readr::read_csv(full_path, progress = FALSE)
})
dplyr::tbl_df(data)
}
#' Creates the name of file
#'
#' This function builds a string with the name of file that will be loaded based on the year of the required information.
#'
#' @param year The year of the required information.
#'
#' @return This function returns the file name that should be loaded.
#'
#' @examples
#' \dontrun{
#' make_filename(2013)
#' }
#'
#' @export
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' Selects all months in each file loaded (year)
#'
#' This function creates a list of all months in the files.
#'
#' @param years a vector with all years that should be loaded
#'
#' @return This function returns a list with the column month of each file.
#' if the year is invalid a warning will be generated to inform it.
#'
#' @details This function uses mutate and select functions from dplyr package.
#' It also calls make_filename function in order to create a string with the filename and
#' fars_read function to load the files in a dataframe of all years specified in the parameter.
#' In case the year required doesn't have a correspondent file it will generate a warning.
#'
#' @examples
#' \dontrun{
#' fars_read_years(c(2013, 2014, 2015))
#' fars_read_years(c(2014))
#' fars_read_years(c(2013, 2015))
#' }
#'
#' @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_(.dots=c('MONTH', 'year'))
}, error = function(e) {
warning("invalid year: ", year)
return(NULL)
})
})
}
#' Summarize how many accidents happend in each month by year
#'
#' This function summarizes the number of occurrencies in each month by year.
#'
#' @param years a vector with all years that should be loaded
#'
#' @return This function returns a dataframe summarizing the numer of accidents in each month of each year.
#' if the year required is invalid a warning will be generated to inform it.
#'
#' @details This function uses bind_rows, group_by and summarize functions from dplyr package
#' and spread function from tidyr package.
#' It also calls fars_read_years function in order to select only month column from each year.
#' In case the year required doesn't have a correspondent file it will generate a warning.
#'
#' @examples
#' \dontrun{
#' fars_summarize_years(c(2013, 2014, 2015))
#' fars_summarize_years(c(2014))
#' fars_summarize_years(c(2013, 2015))
#' }
#'
#' @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_(key_col = 'year', value_col = 'n')
}
#' Plot a graphic indicating the places of each accident that happend in the required year
#'
#' This function plots a map of a state showing the places of each accident that happend in
#' the required year.
#'
#' @param state.num The state id of the required information.
#' @param year The year of the required information.
#'
#' @return This function returns a map of the state indicating the places of each accident that happend
#' in the required year. It also return an error message if there is no file for the year informed
#' in the parameter year or if the state id is invalid.
#' If there no accident has happend in the informed state in the informed year, it will print
#' a message to inform that there is nothing to plot.
#'
#' @details This function uses filter functions from dplyr package, map function from maps package
#' and points function from graphics package.
#' It also calls make_filename function in order to create a string with the filename, based on the
#' year parameter and fars_read function to load the correspondent file with required year in a
#' dataframe.
#' In case of the year required doesn't have a correspondent file, it will stop running and print a
#' message informing that there is no file for the year.
#' In case of the state ID be invalid, it will stop running and print a message informing that the
#' ID informed in the parameter is invalid.
#' If there is no accidents to plot for state ID informed it will print a message to inform that.
#'
#' @examples
#' \dontrun{
#' fars_map_state(1, 2013)
#' fars_map_state(33, 2014)
#' fars_map_state(40, 2015)
#' }
#'
#' @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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