#' This is a function that reads a data file and displays it as a dataframe.
#' @param filename is a character string giving the name of the data file
#' @return This function returns the output of the data file
#' @importFrom readr read_csv
#' @importFrom dplyr tbl_df
#' @details If the file doesn't exist it will result in an error
#' @examples
#' \dontrun{fars_read("data/accident_2013.csv")}
#' @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)
}
#' This function just adds the year to the accident's data format
#' @param year an integer
#' @return This function returs a string with the filename with the year especified
#' @examples
#' \dontrun{make_filename(2013)}
#' @export
make_filename <- function(year) {
year <- as.integer(year)
sprintf("accident_%d.csv.bz2", year)
}
#' This function reads a list of years and returns a list of data.frames.
#' @param years an integer
#' @return This function returs a list of data.frames
#' @importFrom dplyr mutate select %>%
#' @examples
#' \dontrun{fars_read_years(c(2013,2014))}
#' @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)
})
})
}
#' This function reads a list of years and summarizes them.
#' @param years an integer
#' @return This function returs a list of data.frames with the data summarized
#' @importFrom dplyr bind_rows group_by summarize %>%
#' @importFrom tidyr spread
#' @examples
#' \dontrun{fars_summarize_years(c(2013,2014))}
#' @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)
}
#' create a map of fars events given a state number and a year
#' @param state.num is an integer
#' @param year an integer
#' @return This functions returs a map with a point in every place there has been a fatality in a motor vehicle accident
#' @importFrom dplyr filter
#' @importFrom maps map
#' @importFrom graphics points
#' @examples
#' \dontrun{fars_map_state(1,2013)}
#' @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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