map_pub_try

library(tidyverse)

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library(lubridate)
library(scales)

Attaching package: 'scales'

The following object is masked from 'package:purrr':

    discard

The following object is masked from 'package:readr':

    col_factor

library(tidycensus)      # gets census data that we can use to create maps
library(sf)              # helper package for mapping

Linking to GEOS 3.11.0, GDAL 3.5.3, PROJ 9.1.0; sf_use_s2() is TRUE

library(leaflet)         # interactive mapping package
library(usdata)          # this package has a conversion utility for state abbreviations to full names

Choropleth maps

‘Choropleth’ is an obscure-sounding term, but it is a common type of map where regions are different colors according to some statistic. An example that we have all seen is the US electoral map with red and blue states indicating which candidate or party won each state.

Census data

We’ll start out with census data because it has both the maps and the data (population, income, etc.). Later, we’ll separate these steps so we can learn to map any data.

You’ll need a free api key to get census access. Go here to get a key:

http://api.census.gov/data/key_signup.html

Then when you get the API key, put it into the quotes in census_api_key(““). After you run it, delete it so you don’t publish it to rpubs.

census_api_key("")

To install your API key for use in future sessions, run this function with `install = TRUE`.

This gets maps of the states along with population data from the census bureau:

states <- get_acs(geography = "state",               # gets state by state data
                  variables = "B01003_001",          # this is state population
                  geometry = TRUE,                   # gets geometry (the maps)
                  shift_geo = T)                     # shifts Hawaii and Alaska

Getting data from the 2018-2022 5-year ACS

Warning: The `shift_geo` argument is deprecated and will be removed in a future
release. We recommend using `tigris::shift_geometry()` instead.

Warning: • You have not set a Census API key. Users without a key are limited to 500
queries per day and may experience performance limitations.
ℹ For best results, get a Census API key at
http://api.census.gov/data/key_signup.html and then supply the key to the
`census_api_key()` function to use it throughout your tidycensus session.
This warning is displayed once per session.

Using feature geometry obtained from the albersusa package

Please note: Alaska and Hawaii are being shifted and are not to scale.

old-style crs object detected; please recreate object with a recent sf::st_crs()

Let’s take a look at the data we just got. Click on states in the viewer.

The data look a little different from our usual data. But note that it has state names under NAME, it has the population of each state under estimate, and geometry provides the data to create the map. So it includes both the map information and the data (population) that we’re going to map.

Here’s a really simple choropleth map using the data. All it does is take the state data, send it to ggplot, and fill (or color) the states with their population (called estimate).

states |> 
  ggplot() +  
  geom_sf(aes(fill = estimate))