population_density.R

library(tidycensus)
library(tidyverse)

us_county_density <- get_decennial(
  geography = "county",
  variables = "P1_001N",
  year = 2020,
  geometry = TRUE,
  keep_geo_vars = TRUE
) 

us_county_density %>%
  mutate(density = value / (ALAND / 2589988.11)) %>%
  tigris::shift_geometry() %>%
  ggplot(aes(fill = density)) + 
  geom_sf(color = NA) + 
  theme_void(base_size = 11) + 
  scale_fill_viridis_c(trans = "log10") + 
  labs(title = "Population density by county",
       subtitle = "2020 US Census",
       fill = "Persons / sq mi",
       caption = "@kyle_e_walker | tidycensus R package") + 
  theme(plot.margin = unit(rep(0.5, 4), "cm"))

options(scipen = 999)

dallas_density <- get_decennial(
  geography = "tract",
  state = "TX",
  county = "Dallas",
  variables = "P1_001N",
  year = 2020,
  geometry = TRUE,
  keep_geo_vars = TRUE
) %>%
  mutate(density = value / (ALAND / 2589988.11))

mapview::mapview(dallas_density, zcol = "density",
                 layer.name = "Population density<br/>in Dallas County<br/>(people/sq mi)")

# ACS example: population density vs. income in Illinois
illinois <- get_acs(
  geography = "tract",
  variables = c(total_pop = "B01003_001",
                median_income = "B19013_001"),
  state = "IL",
  geometry = TRUE,
  keep_geo_vars = TRUE,
  output = "wide"
) %>%
  mutate(density = total_popE / (ALAND / 2589988.11))

ggplot(illinois, aes(x = density, y = median_incomeE)) + 
  geom_point(alpha = 0.5) + 
  geom_smooth() + 
  theme_minimal() + 
  scale_x_log10() + 
  scale_y_continuous(labels = scales::label_dollar()) + 
  labs(title = "Relationship between tract density and median household income",
       subtitle = "Census tracts in Illinois, 2016-2020 ACS",
       x = "Population density (people / square mile)",
       y = "Median household income",
       caption = "@kyle_e_walker | tidycensus R package")

The section starting on line 27 (dallas_density) gives an error 'Invalid argument name and cannot create file. Any ideas?