Code to create a map of change in US county population, 2013 - 2018, for the 30 Day Map Challenge

movement.R

library(ggplot2)
library(dplyr)
library(tigris)
library(tidycensus)

abbr <- state.abb[-c(2, 11)]
pop2018 <- vector("list", length(abbr))
names(pop2018) <- abbr

for (i in seq_len(length(pop2018))) {
  pop2018[[i]] <- get_acs("county",
                            "B01003_001",
                            geometry = TRUE,
                            state = names(pop2018)[[i]]
                            )
}

state_2018 <- do.call(rbind, pop2018)

pop2013 <- vector("list", length(abbr))
names(pop2013) <- abbr

for (i in seq_len(length(pop2013))) {
  pop2013[[i]] <- get_acs("county",
                            "B01003_001",
                          year = 2013,
                            geometry = TRUE,
                            state = names(pop2013)[[i]]
                            )
}

state_2013 <- do.call(rbind, pop2013)

county_line <- counties(abbr, TRUE)

state_2018 %>% 
  rename(est2018 = estimate) %>% 
  select(GEOID, est2018, geometry) %>% 
  left_join(state_2013 %>% 
              rename(est2013 = estimate) %>% 
              select(GEOID, est2013) %>% 
              sf::st_set_geometry(NULL)) %>% 
  mutate(value = (est2018 - est2013) / est2013) %>%
  arrange(value) %>%
  mutate(idx = row_number()) %>%
  ggplot() +
  geom_sf(aes(fill = idx), color = NA) +
  geom_sf(data = county_line, 
          fill = NA, 
          color = "#F0F0F0", 
          size = 0.03, 
          alpha = 0.05) +
  scale_fill_gradient2(low = "#40004b", high = "#00441b", midpoint = 1698) +
  coord_sf() +
  theme_void() %+replace%
  theme(
    legend.position = "none",
    plot.background = element_rect(fill = "#2c2c2c")
  )

ggsave("22_movement.png", width = 17, height = 9, dpi = 600)