fw_redistricting_demo.R

library(tidycensus) # Make sure you have tidycensus 1.1 or higher
library(redist)
library(sf)
library(tidyverse)
library(tigris) # Make sure you have tigris 1.5 or higher
library(httr)
options(tigris_use_cache = TRUE)

set.seed(123456)

# Grab existing districts from 
# https://mapitwest.fortworthtexas.gov/giszipfiles/POL_COUNCIL_DISTRICTS.zip
fw_districts <- st_read("data-raw/POL_COUNCIL_DISTRICTS/POL_COUNCIL_DISTRICTS.shp") %>%
  select(district = DISTRICT)

vtds_in_fw <- voting_districts(cb = TRUE, state = "TX") %>%
  st_transform(st_crs(fw_districts)) %>%
  st_point_on_surface() %>%
  st_join(fw_districts, left = FALSE) %>%
  st_drop_geometry() %>%
  select(GEOID = GEOID20, district)

fw_vtds <- get_decennial(
  geography = "voting district",
  year = 2020,
  variables = c(
    Total = "P1_001N",
    Hispanic = "P2_002N",
    White = "P2_005N",
    Black = "P2_006N",
    Asian = "P2_008N",
    Multiple = "P2_011N"
  ),
  output = "wide",
  geometry = TRUE,
  state = "TX"
) %>%
  inner_join(vtds_in_fw, by = "GEOID") %>%
  mutate(district = as.integer(district)) %>%
  filter(!row_number() %in% c(78, 293)) %>%
  st_transform(st_crs(fw_districts))# redist can't handle queen's case neighbors

fw_map <- redist_map(fw_vtds, total_pop = Total, ndists = 10)

fw_sol <- redist_smc(fw_map, nsims = 1000)

redist.plot.plans(fw_sol, draws = 1:6, geom = fw_map) 

mat <- get_plans_matrix(fw_sol)

# Solution 6
fw_vtds$district <- as.numeric(mat[,6])

solution6 <- fw_vtds %>%
  select(district, Total:Multiple) %>%
  group_by(district) %>%
  summarize(across(.cols = Total:Multiple,
                   .fns = ~sum(.x, na.rm = TRUE)))

mapview::mapview(solution6, zcol = "district", col.regions = RColorBrewer::brewer.pal(10, "Set1"))