fars_map_state: Plot a map of fatalities in a State

In masabri01/BuildingRPackagesCoursera: Assignment for Coursera Building R Packages

Description

This function can be used to create a map of fatalities in a US State during a year as reported in the FARS database.

Usage

fars_map_state(state.num, year)

Arguments

state.num	State number as coded in the maps package.
year	A scalar year.

Details

This function takes the state number and a year as inputs and performs the following operations on them: - calls the supporting function, make_filename(), with the year to generate a list of MONTH and year, - calls the supporting function, fars_read(), to read the FARS data file with the generated filename, - If the state number (provided as the input parameter) is NOT found in the FARS data file read: stops the execution with a message, "invalid STATE number: xxx". - For a valid STATE number: - calls the filter() function from the dplyr package to extract the data for the STATE number provided, - If no data exists for the state number: prints a message, "no accidents to plot" and returns NULL. - Otherwise: - sets the invalid data for longitude (values greater than 900) and latitude(values greater than 90), if any, to NA, and - with the cleaned, mappable data: - calls the map() function of the maps package to draw the map of the State, and - calls the points() function of the base graphics package to draw points on the longitude, latitude coordinates as documented in the FARS dataset for that year in that State.

Value

This function draws a map of the State and places points on it – one point for EACH fatality that occurred in that State.

Note

Following functions need to be imported: dplyr package: filter(). maps package: map(). graphics base package: points(). Some validaiton is performed in this function as described in the "Details" section.

Examples

## Not run: 
fars_map_state(1, 2014) # Fatalities map for State #1 during 2014

## End(Not run)

masabri01/BuildingRPackagesCoursera documentation built on May 21, 2019, 12:39 p.m.