#' Read file of annual data from US NHTSA Fatality Analysis Reporting System (FARS)
#'
#' This function takes a file name as an arguement, and checks to see of the
#' file exists in the working directory. If the does not exist, execution
#' stops and the error message 'file <filename> does not exist' is returned.
#' Otherwise, the read_csv function from the readr package reads a compressed
#' file that contains comma delimited entries to form a data frame. Progress
#' on the reading of data is suppressed. Column names are taken as the first
#' row in the data file.
#' Using the tbl_df function from the dplyr package, the data frame is
#' converted to a tibble, which is an S3 class object that provides stricter
#' checking and better formatting than a traditional data frame.
#' @param filename A character string corresponding to the target file
#' @return A tibble data frame
#' @importFrom readr read_csv
#' @importFrom dplyr tbl_df
#' @examples
#' 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)
}
#' Create a FARS filename for annual data by integrating the generic name with year
#' Converts the specified year, either as numeric value or character string, and
#' returns a character vector that corresponds to the generic filename with
#' the specified year embedded.
#' @param year A four digit year to specify time period for data compilation.
#' @return A character vector is returned that embeds the specified <year>
#' into the generic file name for FARS data for the corresponding calendar
#' @examples
#' make_filename(2013)
#' make_filename('2013')
#' @export
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' Read one or more years of FARS data and returns a list of one or more tibble tables
#' This function reads a set of annual FARS data corresponding to the years specified
#' in the years vector and returns a list of tibble tables with the MONTH variables
#' from the data file and a variable year corresponding to each element of the
#' input year vector. Errors occur if the data file is not found. Warnings are
#' displayed for invalid years.
#' @param years A vector containing one or more entries corresponding to four-
#' digit codes corresponding to the year.
#' @return This function returns a list of one or more tibble tables having only
#' the original MONTH variable and the variable year from the vector years provided
#' as an imput arguement.
#' The number of elements in the list corresponds to the length of the years
#' vector provided as input
#' @importFrom magrittr %>%
#' @importFrom dplry mutate select
#' @inheritParams make_filename fars_read
#' @export
#' @examples
#' fars_read_years(2013)
#' fars_read_years('2013')
#' fars_read_years(c(2013, 2015))
#' fars_read_years(c(2013:2015))
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 counts of observations by month for one or more tibble table
#' The fucntion vertically concatenates each element of the list of one
#' or more tibble tables corresponding to elements of the years vector
#' and counts the number of accidents by year and MONTH. The table is
#' then converted from long to wide format so that each year forms an
#' individual column indexed by rows from 1 to 12 corresponding to the
#' month number.
#' @param years A vector of one or more four-digit years
#' @return A tibble table of dimension 12 x (1 + length(years))
#' is returned with a summary count of observations.
#' Column names are MONTH and four-digit year values.
#' All values returned are in integer format.
#' @inheritParams fars_read_years
#' @importFrom dplyr bind_rows group_by summarize
#' @importFrom tidyr spread
#' @export
#' @examples
#' fars_summarize_years(c(2013,2015))
#' fars_summarize_years(2013:2015)
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)
}
#' Display map for selected state showing locations of observations
#' Retrieves outline of state or area corresponding to state.num,
#' which must be a valid FIPS code. (See URL below for valid
#' codes.) Error returned for invalid STATE code. Forms file
#' name from generic form and year entered. Attempts to read
#' file in working directory. Error results if file not found.
#' If there are no accident to report, as message is printed,
#' otherwise, locations of accidents are plotted by latitude
#' and longitude.
#' @param state.num is a two-digit integer that corresponds to the
#' FIPS (Federal Information Processing Standards) State Numeric Code
#'....see https://www.census.gov/geo/reference/ansi_statetables.html.
#' @param year is a four-digit year code.
#' @return A map is displayed with the outline of the state or area
#' associated with the state.num, and the locations of accidents
#' in the FARS data file for the corresponding year.
#' @importFrom dplyr filter
#' @importFrom maps map
#' @importFrom graphics points
#' @inheritParams make_filename fars_read
#' @export
#' @examples
#' fars_map_state(12, 2014)
#' fars_map_state('13','2013')
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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