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November 20, 2022 10:05
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#30DayMapChallenge 2022 - Day 21 - Kontur Population Data
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# Compare Kontur Population Grid against Stats NZ grids for Wellington City | |
# For #30DayMapChallenge 2022 - Day 21 | |
library(dplyr) | |
library(sf) | |
library(rmapshaper) | |
library(ggplot2) | |
# Kontur data ----------------------------------- | |
# boy, am I glad I have 64GB of RAM! | |
# kontur_nz <- | |
# readRDS("kontur_nz.rds") | |
# CRS_KONTUR <- st_crs(kontur_nz) | |
# https://data.humdata.org/dataset/kontur-population-dataset | |
kontur <- | |
st_read("kontur_population_20220630.gpkg") | |
CRS_KONTUR <- st_crs(kontur) | |
# https://datafinder.stats.govt.nz | |
ta <- | |
st_read("territorial-authority-2021-clipped-generalised.gpkg") | |
CRS_NZ <- st_crs(ta) | |
nz <- | |
ta |> | |
# Ignore Chathams etc | |
filter(! TA2021_V1_00 %in% c("067", "999")) |> | |
count() |> | |
ms_simplify(keep = 0.02) |> | |
st_transform(crs = CRS_KONTUR) | |
kontur_nz <- | |
kontur |> | |
mutate(is_nz = lengths(st_intersects(geom, nz)) > 0) |> | |
filter(is_nz) | |
saveRDS(kontur_nz, "kontur_nz.rds") | |
rm(kontur); gc() | |
# Stats NZ grids -------------------------------- | |
# https://datafinder.stats.govt.nz/data/category/grids/ | |
sq500 <- | |
st_read("stats_grid/500m/new-zealand-2018-estimated-resident-population-statistical-g.gpkg") | |
sq1000 <- | |
st_read("stats_grid/1000m/new-zealand-2018-estimated-resident-population-statistical-g.gpkg") | |
# Extract Wellington City ----------------------- | |
# And calculate population density, since the shapes aren't the same size | |
wc_geo <- | |
ta |> | |
filter(TA2021_V1_00_NAME == "Wellington City") |> | |
ms_simplify(keep = 0.05) | |
wc_500 <- | |
sq500 |> | |
mutate(is_wc = lengths(st_intersects(geom, wc_geo)) > 0) |> | |
filter(is_wc) |> | |
mutate(grid_area = geom |> st_area() |> as.numeric(), | |
pop_density = ERP / grid_area * 1000000) | |
wc_1000 <- | |
sq1000 |> | |
mutate(is_wc = lengths(st_intersects(geom, wc_geo)) > 0) |> | |
filter(is_wc) |> | |
mutate(grid_area = geom |> st_area() |> as.numeric(), | |
pop_density = ERP) | |
wc_kontur <- | |
kontur_nz |> | |
mutate(is_wc = | |
lengths( | |
st_intersects( | |
geom, | |
wc_geo |> st_transform(crs = CRS_KONTUR) | |
)) > 0) |> | |
filter(is_wc) |> | |
st_transform(crs = CRS_NZ) |> | |
mutate(grid_area = geom |> st_area() |> as.numeric(), | |
pop_density = population / grid_area * 1000000) | |
# Map ------------------------------------ | |
MAP_FONT <- "Sans" | |
SHIFT_LEFT <- c(-25000, 0) | |
SHIFT_RIGHT <- c(25000, 0) | |
shift_map <- | |
function(df_sf, shift_xy) { | |
df_sf |> | |
mutate(geom = st_geometry(df_sf) + shift_xy) |> | |
st_set_crs(CRS_NZ) | |
} | |
ggplot() + | |
geom_sf(data = wc_geo, | |
aes(geometry = geom), | |
linewidth = 2, colour = "black", fill = NA) + | |
geom_sf(data = wc_geo |> shift_map(SHIFT_LEFT), | |
aes(geometry = geom), | |
linewidth = 2, colour = "black", fill = NA) + | |
geom_sf(data = wc_geo |> shift_map(SHIFT_RIGHT), | |
aes(geometry = geom), | |
linewidth = 2, colour = "black", fill = NA) + | |
geom_sf(data = wc_1000, | |
aes(geometry = geom, fill = pop_density), | |
colour = "black", linewidth = 1, | |
alpha = 0.9) + | |
geom_sf(data = wc_500 |> shift_map(SHIFT_RIGHT), | |
aes(geometry = geom, fill = pop_density), | |
colour = "black", linewidth = 1, | |
alpha = 0.9) + | |
geom_sf(data = wc_kontur |> shift_map(SHIFT_LEFT), | |
aes(geometry = geom, fill = pop_density), | |
colour = "black", linewidth = 1, | |
alpha = 0.9) + | |
geom_text( | |
aes(x = 1740000, y = 5440000, geometry = NULL), | |
label = "Stats NZ\nStatistical Grid\n1km prototype", | |
size = 6, colour = "black", hjust = 0.5, | |
family = MAP_FONT | |
) + | |
geom_text( | |
aes(x = 1740000 + SHIFT_RIGHT[1], y = 5440000, geometry = NULL), | |
label = "Stats NZ\nStatistical Grid\n500m prototype", | |
size = 6, colour = "black", hjust = 0.5, | |
family = MAP_FONT | |
) + | |
geom_text( | |
aes(x = 1740000 + SHIFT_LEFT[1], y = 5440000, geometry = NULL), | |
label = "Kontur\nPopulation Density\n400m H3", | |
size = 6, colour = "black", hjust = 0.5, | |
family = MAP_FONT | |
) + | |
scale_fill_viridis_c(guide = guide_colorbar( | |
barwidth = 15, barheight = 0.5, | |
title = "Population per square km", title.position = "top", | |
title.hjust = 0.5 | |
)) + | |
labs(title = "Wellington City Population Density") + | |
coord_sf(datum = NULL) + | |
theme_void(base_family = MAP_FONT) + | |
theme(legend.position = "bottom", | |
plot.background = element_rect(fill = "white", colour = "white"), | |
panel.background = element_rect(fill = "white", colour = "white"), | |
plot.title = element_text(hjust = 0.5, family = MAP_FONT, | |
size = 62)) |
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