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COURSERA: BUILDING R PACKAGES

For more information, see the source links (US NHTSA offial site and Wikipedia):
https://www.nhtsa.gov/research-data/fatality-analysis-reporting-system-fars
https://en.wikipedia.org/wiki/Fatality_Analysis_Reporting_System

Function fars_read

Import: From readr read_csv Main dependencies: dplyr tbl_df

Parameters: filename A character string with the name of the file to read, see notes.

A data frame with data readed from the csv file, or an error if the file does not exists.

Open file related with the accident data files 2013-2015 Function fars_read can read .csv files and .csv archived in .bz2 format and other formats compatible for the basic readr package for its function read_csv Note that in the accidents data set only years 2013, 2014, and 2015 exist. Parameters: filename - name of the file (may be written with the path). The filename argument/input for the function is a string with the name of the file to be opened Function fars_read returns a tibble MxN where M - number of observations; N - number of columns (50 for the accidents data files) Usage: fars_read(filename) Examples:

print("Don't run me")
#dontrun{
library(dplyr)
library(readr)
setwd("C:/Users/Your_Path/")
dataf = fars_read("accident_2013.csv.bz2")
dataf = fars_read("C:/Users/Your_Path/accident_2013.csv.bz2")
head(dataf)
#dontrun}

Function: make_filename

Note: To generate file name use: For help use:make_filename} Details: In case if the file does not exist an error message is produced and execution stops. Open code:

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 data file name

Make .csv data file name related to the given The function does not check if the file is available.

Parameters: year A string or an integer with the input

This function returns a string with the data file name for a given year, and the file path within the package.

Examples:

#dontrun{
make_filename(2012)

s accident_2012.csv.bz2
# For help use: 
?fars_read
# Open code:
make_filename <- function(year) {
       year <- as.integer(year)
       system.file("extdata",
                   sprintf("accident_%d.csv.bz2", year),
                   package = "fars",
                   mustWork = TRUE)
}
#dontrun}

Function fars_read_years

Used to read the FARS years Ancillary function used by fars_summarize_years Primary function to the Parameters: years A vector with a list of years Main dependencies: dplyr mutate_ Main dependencies: dplyr select_ Main dependencies: magrittr “%>%” A data.frame including entries in data by month, or NULL if the year is not valid For help use: ?fars_read For help use: ?make_filename For help use: ?fars_summarize_years Examples:

 #dontrun{
 setwd("C:/Users/Your_Path/")
 fars_read_years(2013)
 
# Open code:
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)
              })
      })
}
#dontrun}

Function fars_summarize_years

Summarize FARS data by years

This simple function summarizes yearly accidents data, by month Parameters: years A vector with a list of years to summarize by.

A data.frame with number of accidents by years summarized by month Main dependencies: dplyr bind_rows Main dependencies: dplyr group_by_ Main dependencies: dplyr summarize_ Main dependencies: tidyr spread_ Main dependencies: magrittr “%>%” For help use: ?fars_read_years Examples:

 #dontrun{
 setwd("C:/Users/Your_Path/")
 plot(fars_summarize_years(2013))
 fars_summarize_years(c(2013, 2015))

# Open code: 
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")
}
 #dontrun}

Function fars_map_state

Display accidents map by state and year

Displays a plot with a state map including the accidents location by year If the is invalid the function shows an error Parameters: state.num An Integer with the State Code (alphabetical order) Parameters: year A string, or an integer, with the input

Main dependencies: maps map Main dependencies: dplyr filter_ Main dependencies: graphics points For help use: ?fars_read ?make_filename References 2014 FARS/NASS GES Coding and Validation Manual Examples:

 \dontrun{
 fars_map_state(37, 2014)
 
# Open code:
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$STATE))) {
  stop("invalid STATE number: ", state.num)
}
data.sub <- dplyr::filter_(data, .dots = paste0("STATE==", state.num))
if(nrow(data.sub) == 0L) {
  message("no accidents to plot")
  return(invisible(NULL))
}
is.na(data.sub$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)
})
}
# dontrun}

Function catfunction

This function allows you to express your love of cats. Asks question: Do you love cats? Defaults to TRUE. Examples:

 cat_function()

path = "C:/Users/Your_Path/"
subfolder = "inst/extdata/"
myfile = "accident_2015.csv.bz2"
mydata <- fars_read(paste0(path, subfolder, myfile))
head(mydata[ , 1:8], 10)

#> Warning: `tbl_df()` is deprecated as of dplyr 1.0.0.
#> Please use `tibble::as_tibble()` instead.
#> This warning is displayed once every 8 hours.
#> Call `lifecycle::last_warnings()` to see where this warning was generated.

fars_map_state(39, 2015)
fars_map_state(29, 2015)

#> Warning: `filter_()` is deprecated as of dplyr 0.7.0.
#> Please use `filter()` instead.
#> See vignette('programming') for more help
#> This warning is displayed once every 8 hours.
#> Call `lifecycle::last_warnings()` to see where this warning was generated.

output:
  rmarkdown::html_vignette:
    fig_caption: yes