2020-12-17_mapbaltimore_park-walking-distance-map.R

library(sf)
library(mapbaltimore)
library(tidyverse)

map_theme <- ggplot2::theme(
    panel.grid.major = ggplot2::element_line(color = "transparent"),
    axis.title = ggplot2::element_text(color = "transparent"),
    axis.text = ggplot2::element_text(color = "transparent")
  )

buffer <- 1
buffer <- units::set_units(buffer, m)

selected_area_neighborhoods <- c("Baltimore Highlands", "Ellwood Park/Monument")

# alternate selected neighborhood for central Baltimore
# selected_area_neighborhoods <- c("Harwood")

selected_area <- get_area(area_type = "neighborhood",
                          area_name = selected_area_neighborhoods) %>% 
  st_transform(4326)

# Context neighborhoods are only used to overall size of the map
context_area_neighborhoods <- c("Greektown",
                                "CARE",
                                "Milton-Montford",
                                "Canton",
                                "Butcher's Hill",
                                "Brewers Hill")

# alternate context for central Baltimore
# context_area_neighborhoods <- c("Charles Village", "Oakenshawe", "Greenmount West", "Remington", "East Baltimore Midway", "Charles North")

context_area <- get_area(area_type = "neighborhood",
                         area_name = context_area_neighborhoods,
                         union = TRUE)

context_area_bbox <- context_area %>% 
  st_transform(4326) %>% 
  st_bbox()

arterial_streets <- streets %>% 
  filter(sha_class %in% c("MART", "PART", "FWY")) %>% 
  st_union() %>% 
  st_transform(4326)

area_arterial_streets <- arterial_streets %>% 
  st_crop(context_area) %>% 
  st_transform(4326)

area_park_isochrones <- park_isochrones %>% 
  st_transform(4326)

area_parks <- parks %>% 
  st_crop(context_area)

context_area_footways <- osmdata::opq(bbox = context_area_bbox) %>%
  osmdata::add_osm_feature(key = "highway", value = "footway") %>%
  osmdata::osmdata_sf()

area_park_entrances <- context_area_footways$osm_lines %>% 
  st_transform(2804) %>% 
  st_crop(st_buffer(context_area, buffer*150)) %>% # Crop footways to within 150m of the context area
  st_intersection(st_buffer(parks, buffer*2)) %>% # Crop footways to within 2m of parks in the area
  st_difference(st_union(parks)) %>% # Remove footways within parks
  st_centroid() %>% # Find center point of lines
  select(name, geometry) %>% 
  st_transform(4326)

area_park_corners <- parks %>%
  st_crop(st_buffer(context_area, buffer*150)) %>% 
  st_convex_hull() %>%
  st_simplify(dTolerance = 0.06) %>% 
  st_cast(to = "MULTIPOINT") %>% 
  st_cast(to = "POINT") %>%
  select(name, geometry = geoms) %>%
  st_transform(4326)

area_parks <- area_parks %>% 
  st_transform(4326)

area_parks_center <- parks %>% 
  st_crop(st_buffer(context_area, buffer*150)) %>% 
  st_centroid() %>% 
  select(name, geometry = geoms) %>%
  st_transform(4326)

area_park_isochrones_points <- bind_rows(area_park_corners,
                                         area_park_entrances,
                                         area_parks_center)

area_park_isochrones <- mapboxapi::mb_isochrone(
  area_park_isochrones_points,
  time = c(3, 6, 9),
  profile = "walking")

park_isochrones <- area_park_isochrones %>% 
  group_by(time) %>% 
  summarise(
    geometry = st_union(geometry)
  ) %>% 
  mutate(
    time_alpha = case_when(time == 3 ~ 0.3,
                           time == 6 ~ 0.2,
                           time == 9 ~ 0.1)
  ) %>% 
  st_transform(4326)

ggplot() +
  geom_sf(data = arterial_streets,
          color = "gray80") +
  geom_sf(data = park_isochrones,
          fill = "lightgreen",
          color = "gray30",
          linetype = "dotted",
          aes(alpha = time_alpha)) +
  geom_sf(data = selected_area,
          fill = NA,
          color = "gray20",
          linetype = "longdash") +
  geom_sf(data = area_parks,
          fill = "lightgreen",
          color = "darkgreen") +
  coord_sf(xlim = c(context_area_bbox[[1]], context_area_bbox[[3]]),
           ylim = c(context_area_bbox[[2]],context_area_bbox[[4]])) +
  guides(alpha = "none") +
  labs(
    title = "Walking distance (3, 6, and 9 minutes) from southeast Baltimore parks"
  ) +
  hrbrthemes::theme_ipsum_rc() +
  map_theme